Reflexes- they are involuntary stereotyped responses to stimuli, they involve the brain, spinal cord, and peripheral nerves
Spinal cord- cylinder nervous tissue that begins at the foramen magnum and passes through the vertebral canal as far as the inferior margin of the first lumbar vertebrae (L1), 18 inches long and ½ inches wide
Anterior Median Fissure- in the front, deeper
Posterior Median Sulcus- in the back, shallow
▪Two Enlargements for Limbs: (up and down below)
1. Cervical Enlargement- in the inferior cervical region, the spinal cord gives rise to the nerves of the upper limbs, up
2. Lumbar Enlargement- in the lumbosacral region there are nerves to the pelvic region and lower limbs arise, below
Medullary Cone- the spinal cord becomes more tapered
▪Meninges- the spinal cord and brain are enclosed in three fibrous membranes, specialized membranes that surround the spinal cord
A. shock absorption
B. physical stability
C. blood vessels that branch within these layers to provide oxygen and nutrients
1. Dura Mater- outer most layer, forms a loose fitting sleeve called the dural sheath around the spinal cord, though and fiborous, it will fuse with the periosteum of the occipital bone around the formamus magnum
Coccygeal Ligament- inferiorly the dura mater will blend with the filum terminal, longitudinal support
-horizontally there is stability by fusing with connective tissue of the spinal nerve such that the dura mater will extend out of the IVF
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1.Describe the functional anatomy of the spinal cord using the following terms: white matter, gray matter, tracts, roots and spinal nerves. The spinal cord consists of a superficial White matter and a deep Gray matter. The white matter consists of myelinated axons, which form nerve tracts and the Gray matter consists of neuron cell bodies, dendrites and axons. The white matter in each half of the ...
Epidural Space- the space between the sheath and the vertebrae bone, the space between the dura and the wall of the vertebral canal, it has loose connective tissue, blood vessels and adipose tissue
2. Arachnoid Mater- adheres to the dural sheath, it consists of a simple squamous epithelium, the arachnoid membrane
Subarchnoid Space- a loose mesh of collagenous and elastic fibers spanning the gap between the arachnoid membrane and the pia mater, it’s filled with cerebrospinal fluid (CSF), a clear liquid
Pia Mater- inner most; a delicate, translucent membrane that closely follows the contours of the spinal cord
Filum Terminal- this continues beyond the medullary cone and is a fibrous strand
3. Cauda Equina- surrounded by CSF, the lumbar enlargement and medullary cone give rise to a bundle of nerve roots that occupy the canal of the vertebrae L2 to S5 (segments), it has a resemblance to a horse tail and it innervates the pelvic organs and lower limbs, region inferior to the L1 and L2, consists of dorsal and ventral roots
-31 pairs of spinal nerves
-8 cervical nerves (C1-C8)
-12 thoracic (T1-T12)
-5 lumbar (L1-L5)
-5 sacral (S1-S5)
-1 coccygeal (Co)
Ganglia- the cell bodies of sensory neurons that are located at each segment
Dorsal Root Ganglia- (toward the back, spinal) they lie between the pedicles of the adjacent vertebrae, the axons that are appropriated to the dorsal root ganglia are the dorsal roots and send sensory information to the CNS
Ventral Roots- axons of motor neurons, they both pass through the intervertebral foramen (IVF)
-they are distal to the ganglion
-dorsal and ventral roots are formed together and this forms the spinal nerves which are also called mixed nerves
*dorsal is posterior and you have information coming in; sensory
*anterior is ventral and you information going away (to); motor commands
-the spinal cord will grow until age four
-the spinal column will continue growing
-there is loose correlation between the segment and the nerve
-spinal nerves elongate and the sacral segments of the spinal cord are located at the C1 and L2 area
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Denticulate Ligaments- extend from the pia mater to the dura mater and are on both sides and prevents lateral movement
Anterior/Posterior Median Fissure- mark the left and right sides of the spinal cord
White Mater- mylinated axons, more superficial
Gray Mater- unmylinated and contains cell bodies of neurons, surrounds central canal and forms horns that project outward both posterior and anteriorly
-the cells bodies of neurons are organized into nuclei:
Sensory Nuclei- receive and relay sensory information from peripheral receptors, posterior or dorsal
Motor Nuclei- issue motor commands to peripheral motor effectors, anterior or ventral
-if you cut it in half you cut the sensory and motor nuclei
(Information comes through the back door and motor commands through the front door)
▪Gray Mater:
Posterior Gray Horns- somatic visceral sensory nuclei
Anterior Gray Horns- somatic motor nuclei, lateral gray horns, they are found in the thoracic and lumbar regions and contain visceral motor nuclei
Gray Commisure- connects the right and left sides of the central canal, located posterior and anterior to the central canal and allows for crossover
▪White Mater:
Posterior White Column- they lie between the posterior gray horns and the posterior median sulcas
Anterior White Column- they lie between the anterior gray horns and the posterior median fissure
Lateral White Column- white mater between the anterior and posterior columns on each side
Anterior White Commisure- it interconnects the anterior white columns
Funiculi- another name for columns
Fasciculus/Tract- bundle of axons in the central nervous system that are fairly uniform with respect to diameter, mylination, and conduction speed
-all axons within a tract relay the same type of information (sensory or motor)
Ascending Tract- carries sensory information toward the brain and enters through the posterior side, sends it up the spinal cord
Descending Tract- sends motor commands to the spinal cord through the anterior side, down
▪Spinal Nerves:
Nerves- a cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue
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Spinal Nerves- are covered in connective tissue, just like muscles
Three Layers of Spinal Nerves:
1. Epineurium- outermost layer, it covers the peripheral nerves, dense, irregular fibrous connective tissue and protects the nerve from stretching and injury
2. Perineurium- middle layer, divides the peripheral nerves into compartments called fasicles
Fasicles- nerve fibers that are gathered in bundles, contain bundles of axons
-each is wrapped in a sheath called perineurium
3. Endoneurium- inner most layer, surrounds the individual axons, a thin sleeve of loose connective tissue
-external to the neurilemma or shwann cells
-arteries and veins in the epineurium and perineurium have capillaries that branch out into the endoneurium to supply the axons and shwann cells
-dorsal and ventral roots are rooted to the spinal canal, they are the shortest in the cervical region and become longer inferiorly, they travel through the IVF and when you get down to L2 (coccyx) they form a cauda equina and they merge to form spinal nerves
Branches in our spinal nerve include:
1. Dorsal Ramus- will carry sensory and motor information from the skin muscles and joints to the back
2. Ventral Ramus- carries sensory and motor information from the ventral/lateral body surface to the muscles of the trunk
Dermatome- specific region of the skin surface that is monitored by a single pair of spinal nerves, each spinal nerve except C1 receive sensory input from this area of skin
▪Nerve Plexus- ventrial rami of adjacent spinal nerves that blend their fibers and produce compound nerve trunks
Four Nerve Plexus’s:
1. Cervical Plexus- ventrical rami from cervical C1 to C5, it innervates muscles of the neck and diaphragm
Phrenic Nerve- the nerve that provides information to the diaphragm
2. Brachial Plexus- consists of the ventral rami C5 to T1, innervates the pectoral girdle and upper limbs, near the shoulder
3. Lumbar Plexus- it consists of the ventral rami from T12 to L4, it innervates the pelvic girdle and lower limbs, the lower back
4. Sacral Plexus- the ventral rami from L4 to S4, innervates the pelvic girdle and lower limbs, lower back
5. Coccygeal Plexus- it’s adjacent to the lower sacrum and coccyx
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This report analyzes the primary internal and external influence on the General Motors Corporation and the influence of changing political environment on policy making and response of the corporation. Then the report discusses the changing political environment in and its influence. The influences of political environment on policies and decision making to the corporation are analyzed. The ...
▪Reflexes- are rapid responses to certain/specific stimuli, quick, involuntary, and are stereotyped reactions of glands or muscles to stimulation (will occur/respond the same way every time)
Neural Reflex- sensory fibers that deliver information to the CNS and motor fibers that carry the motor commands to the peripheral effectors
Reflex Arch- wiring of a single reflex, begins at receptor and ends at the peripheral effector
Step 1- arrival of a stimulus and activation of a receptor
-you have receptors that get changes in pain, temperature, and pressure
-detect changes in internal and external environments Example: put your hand down on a tack
Step 2- the activation of a sensory neuron, the message is being sent through sensory neurons
Step 3- information processing in CNS, a neurotransmitter (ACH) is released at the synapse
-the interneurons can coordinate a response and they can stimulate some neurons and inhibit others
-some sensory neurons will stimulate a motor neuron directly
Step 4- the activation of a motor neuron, an action potential is sent into the periphery through the ventral root
Step 5- response to a peripheral effector
▪Classify Reflexes: Development
Innate Reflexes or Acquired Reflexes:
Innate Reflex- genetically or developmentally programmed such as withdrawal from pain or infant reflexes
Acquired Reflex- more complex learned reflexes, they are rapid and automatic but they are learned instead of pre-established, this type of reflex is enhanced my repetition Example: driving or any athletic skills
▪Classify Reflexes: Processing Cites
Spinal Reflex or Cranial Reflex
Spinal Reflex- processed in spinal cord
Cranial Reflex- processed in the brain, response to a bright light or sudden noise
▪Classify Reflexes: Nature of Response
Somatic Reflex or Visceral Reflex
Somatic Reflex- are the involuntary control of the muscular system
Visceral Reflex- are the automatic/autonomic reflexes that control the activities of other systems
▪Classify Reflexes: Complexity of the Circuit
Monosynaptic or Polysynaptic
Monosynaptic- sensory nerve to the motor nerve (directly), there are no interneurons so you will have a minimized response time
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Chad Stein PS 101 Dr. Rom 1. Gazzaniga, M. S. "One Brain or Two" Scientific American. 1967. Rpt. In Forty Studies That Changed Psychology. Ed. Roger R. Hock. Englewood Cliffs: Prentice Hall, 1995. 2-11. 2. This article dealt with experiments that showed the different functions of the right and left hemisphere of the brain. It also described the functions of the left and right hemisphere. "Your ...
Polysynaptic- many synapse, longer delay between the stimulus and the response, there are interneurons that can give a more complicated response
▪Specific Reflexes
Monosynaptic:
Stretch Reflex- automatic regulation of skeletal muscle length, the stimulus will activate a sensory neuron which will trigger an immediate motor response, has to be inhibited Example: Patellar Reflex
Postural Reflex- reflexes that maintain posture, some can be stretch reflexes or polysynaptic reflexes, they are fine adjustments that are being made at any given time
▪Specific Reflexes
Polysynaptic Reflex:
Golgitendon Reflex- monitors the external tension that is produced during a muscular contraction and prevents breaking or tearing of tendons
Receptors/Golgitendon Organs- they detect tension in the tendon and this information is sent to the CNS, at which point interneurons will inhibit the motor neurons to prevent a muscle from tearing its tendon
Withdrawal Reflex- you’ll move a body part away from a particular stimulus, it is more complicated than a monosynaptic reflex, impulses can be carried up and down the spinal cord for a more complicated response (involve many levels) Example: pain
Flexor Reflex-type of withdrawal reflex, moves a limb away from the source of pain, this flexes the hamstrings
-sensory neurons bring that information into the spinal cord where they activate internuerons to make coordinated responses
Reciprocal Inhibition- one set of motor neurons stimulating the motor neurons that control the antagonistic muscles, a reflex phenomenon that prevent muscles from working against each other
Crossed Extensor Reflex- control contralateral reflex arch in that the motor response occurs on the other side of the body
-it will compliment the flexor reflex, this response will stiffen your opposite leg to support your body weight when you lift the one leg off of the floor
-contraction of the extensor muscles in the limb opposite from the one that is withdrawn
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Ipsilateral Reflex- same side of the body
Outline
The Brain and Cranial Nerves-Chapter14
-the adult human brain has about 98% of neural tissue and weighs 3 pounds
-male have a 10% larger brain, due to bigger body size
-this has no correlation with brain size and intelligence
▪Major Landmarks and Regions
Cerebrum- largest region of the brain, divided into the left and right cerebral hemispheres, these hemispheres are separated by a longitudinal fissure and they are connected by a band of white matter called the corpus callosum, its highly folded surface increases surface area, it is covered by cerebral cortex and deals with conscious thought, sensation, intellect, memory, and complex movement
Corpus Callosum- think bundle of nerve fibers, C-shaped band of nerve tracts that connect the right and left cerebral hemispheres to each other
Cerebral Cortex- contain elevated ridges called gyri separated by deep grooves called fissures and shallow depressions called sulci, the structure of the gyri will increase surface area
Cerebellum- is seen from the posterior, divides into two right and left cerebellar hemispheres, helps maintain posterior and controls fine
movements, it adjusts ongoing movements by comparing arriving sensations experienced previously and this allows you to perform the same movements repeatedly
Diencephalon- composed of right thalamus, hypothalamus, and the enphendibulum, link between the cerebrum and brain stem
Enphendibulum- connects t he hypothalamus to the pituitary gland, this is the link between the nervous and endocrine system, also the link between the cerebral hemisphere and brain stem because the pituitary gland is part of the endocrine system
▪The Brain Stem consists of different parts:
1. Mesencephalon- also called the midbrain, processes visual and auditory information, controls reflexes that are triggered by visual or auditory stimuli
Example: turning your head when hearing a loud noise
2. Pons- connects the cerebrum to the brain stem, contains nuclei that deal with somatic and visceral motor control particularly with respiration, the basic respiration rate originates in the medulla oblongata and the pons regulate it, links the cerebral hemisphere to the mesensepahlon, diencephalon
3. Medulla Oblongata- connects to the spinal cord, relays sensory information to the thalamus and other areas in the brain stem, regulates autonomic function with the cardiac center which adjust the heart rate and the vasomotor center which regulates blood pressure volume through peripheral tissues, digestion and the pace of respitory movements which then are regulated by the pons
▪Ventricles:
One, Two, Three, Four
1. Each cerebral hemisphere has one lateral ventricle which are ventricles 1 & 2
-lateral ventricles (2 ventricles) are separated by septumpellucidum and form a large arch in each cerebral hemisphere
2. Ventricles 1 &2 are connected to ventricle 3 by the interventricular foramen/the foramen of monro
3. The 3rd ventricle is located in the diencephalon; the 3rd ventricle connects to the 4th ventricle by the mesencephalic aqueduct/aqueduct of cilvias/cerebral aqueduct
4. The 4th ventricle lies between the pons and the cerebellum then extends into the medulla oblongata, central canal and spinal cord
-the ventricles are filled with cerebrospinal fluid (CSF) which circulates in the subarachnoid space via the foremena in the roof of the 4th ventricle so that the CSF can surround the cranial nerves
▪Protect and Support in the Brain:
A. Bone of the Cranium (8)
1. Occipital 5. Sphenoid
2. Parietal (Right and Left) 6. Ethmoid
3. Frontal
4. Temporal (Right and Left)
-the cranial bones are connected to dense connective tissue, are immovable joints called sutures
Four Types of Sutures:
1. Lamboidal Suture- is in the posterior which separates the occyput from the parietal bones from the parietal bones
2. Coronal Suture- connects the frontal bone to the parietal bones
3. Sagittal Suture- separates the parietal bones
4. Squamous Suture- separates the temporal bones to the parietal bones
B. Cranial Meninges:
Dura Mater- outer layer that is fused to the periosteum which is called the endostial layer
-no epidural space as there is in the spinal cord
Arachnoid Meninge- middle layer, covers the brain but does not follow the underline fold, provides a smooth surface and contacts the inner layer of the dura mater, it extends between the arachnoid membrane and the pia mater
Pia Mater- sticks to the surface of the brain and around every fold and each penetrating blood vessel
Dural Fold- provide stabilization and support to the brain
Inner Meningial Layer- extend into the cranial cavity like a sheet, inner meningial layer is separated by an outer layer that contains fluids and blood vessels including the venus sinesus that open to the internal jugular veins in the neck
Dura Sinuses- are large collecting veins between the layers of a dural fold
Three Largest Dural Folds:
1. Falxcerebri- located between the cerebral hemisphere in the longitudinal fissure
2. Tentorium Cerebelli- separates the cerebellar hemispheres from the cerebrum
3. Falxcerebelli- it is between the cerebellar hemispheres
C. Cerebrospinal Fluid (CSF) – it surrounds the exposed surfaces of the CNS, cushions the neural structures and supports the brain, transports nutrients, chemical messengers and waste products
Choroid Plexus- produces CSF, made of specialized ependymial cells and permeable capillaries
-the ependymial cells secrete the CSF into the ventricles and remove the waste products from the CSF
-it is located at the floors of the of the ventricles 1 & 2 (lateral), through the foramen of monro and on the floor of the ventricles 3 & 4
-the composition of the CNS is closely monitored, CSF reaches the subarachnoid space through the holes in the roof of ventricle 4
-there are two lateral apertures and a median aperture which allows the CSF to flow through the subarachnoid space surrounding the brain, spinal cord and cauda aquina
D. blood brain Barrier:
Supply to the Brain and Blood Brain Barrier:
-supply and nutrients and oxygen which is met by an extensive blood supply
-the arterial blood supply is through the internal carotid arteries and vertebral arteries
-blood leaves the brain through the internal jugular veins which drains the dural sinuses
Blood Brain Barrier:
-it isolates the neural tissue from the general circulation
Endothelial Cells- they line the capillaries in the CNS and they are connected by tight junctions to prevent diffusion
-the lipid soluble compounds diffuse through the membrane, water and ions must pass through channels and larger compounds pass through active/passive transport
Astrocytes- most numerous, neuroglia in the CNS cover the outer surfaces in the endothelial cells, they release a chemical that can control the permeability of the endothelium, therefore they help maintain the blood brain barrier
-their capillaries at the choroid plexus have specialized ependymial cells that monitor their permeability
-the gray mater is in the cortex and nuclei
-the white mater is deep to the cortex and around the nuclei
Central Sulcas- divides the frontal lobe from the parietal lobe
Lateral Sulcas- separates the frontal lobe from the temporal lobe
Parietal Occipita Sulcas- separates the parietal lobe from the occipital lobe
-each 8 cerebral hemispheres receive sensory information and sends motor commands to the opposite side of the body
-the two hemispheres have different functions even though they look identical
▪White Mater of the Cerebrum-Interior
Three Types of Fibers:
1. Association Fibers- they interconnect neural cortex with a single cerebral hemisphere
A. Arcuate Fibers- go from one gyris to another
B. Longitudinal Fasiculi- longer than arcuate and go from the frontal love to other lobes of the hemisphere
2. Commissural Fibers- interconnects the cerebral hemisphere and allows communication between them
-this will include the corpus callosum
3. Projection Fibers- link the cerebral cortex to the diensephalon, brain stem, cerebellum and spinal cord
▪Motor and Sensory Areas of the Cortex:
1. Central Sulcas- separates the motor and sensory areas of the cortex
2. Pre-Central Gyris- it is anterior to the central sulcas, primary motor cortex, directs voluntary movements by controlling somatic motor neurons in the brain stem and spinal cord such that you stimulate a motor neuron in this primary motor cortex so you can get a contraction (front door)
3. Post-Central Gyris- posterior to the central sulcas, primary sensory cortex (back door)
4. Visual Cortex- in occipital lobe and gets visual information
5. Auditory Cortex- in temporal lobe and receives hearing information
6. Ol-Factory Cortex- in temporal lobe and has smelling information
▪Thalamus:
Cerebral Nuclei- masses of gray mater deep in each hemisphere that direct activities at a subconscious level, particularly subconscious control of the skeletal muscle
-nuclei can alter motor commands issued by the motor cortex
Example: when you walk the nuclei control your arm and thigh movements that occur between the time the start and stop commands are issued
Diensephalon- all sensory information goes to the thalamus before ascending to the cerebrum
-the thalamus filters the information and passes only selected information on (switching station)
-it also coordinates the activities of the cerebral nuclei and the cerebral cortex b y relaying information between them
▪Hypothalamus- contains important control of the autonomic and endocrine systems, it controls appetite, thirst, body temperature, extends inferiorly to the hypothalamus to the infundibulum which is a stalk that connects to the pituitary gland, can release regulating hormones that are transported by a specialized capillary network
Other Functions of the Hypothalamus:
1. Subconscious control of skeletal muscles, especially those associated with rage, pleasure, pain, or sexual arousal Example: Facial expressions
2. Control of autonomic functions adjust and coordinates activities in the medulla oblongata that control heart rate, blood pressure, and respiration
3. Coordinates actions of the nervous and endocrine systems
4. Secretion of hormones pass through the axons to the posterior pituitary where they are released into circulation Example: Anti-diuretic hormone
5. Production of emotions or drives of thirst or hunger
6. Coordinate between voluntary and autonomic functions such that when you think about a dangerous situation your heart rate will increase
7. Regulates body temperature and can send the message to the vasomotor center and to the medulla oblongata to open or to minimize the diameter to prevent heat loss, blood pressure
8. Control of the day and night cycle (circadian rhythms)
Superior Colliculi- control reflex movements of the eyes, head and neck to visual stimuli such as a bright light
Inferior Colliculi- control movement of the head, neck, and trunk in response to auditory stimuli such as a loud noise