Nervous System

Question 1

Describe the organization of the mammalian nervous system.

Answer 1

-nervous system is divided anatomically into the central nervous system (CNS) and peripheral nervous system (PNS)
-CNS consists of the brain and spinal cord
-PNS includes cranial nerves that arise from the brain and spinal nerves that arise from the spinal cord

Question 2

Identify components of the central nervous system.

Answer 2

The nervous system is composed of the brain and spinal cord. The brain is composed of neurons and support cells (ex. microglia, oligodendrocytes)

Question 3

Describe the organization of the brain and identify its embryological development and origins.

Answer 3

-brain is developed from the ectoderm, one of the 3 germ cell layers in the embryo
-groove appears in the ectoderm that deepens and fuses together to form a neural tube
-part of the ectoderm where the fusion occurs becomes a separate structure call the neural crest
-neural tube becomes the CNS and the neural crest forms the PNS
-4th week after contraception, anterior end of the neural tube has 3 distinct swellings for the forebrain, midbrain, and hindbrain
-5th week, forebrain divides into 2 regions, the midbrain remains unchanged and the hindbrain divides into 2 regions

Question 4

Discuss the basic form and function of the telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon.

Answer 4

Telencephalon (cerebrum): division of the forebrain (prosencephalon), develops into the cerebral hemispheres and lateral ventricles; consists of 4 lobes of cerebral cortex, subcortical white matter, and basal nuclei; controls voluntary movements
Diencephalon: division of the forebrain, develops into the thalamus, hypothalamus, subthalamus, epithalamus, and encloses the 3rd ventricle; processing centre for sensory information and coordinating endocrine system with nervous system
Mesencephalon (midbrain): connects pons and cerebellum, develops from midbrain and remains as midbrain and aqueduct; relay system, transmitting information necessary for vision and hearing, motor movement, pain, sleep/wake cycle
Metencephlon: part of hindbrain that differentiates into pons and cerebellum, and 4th ventricle; sensory innervation to the face and mandible
Myelencephlon: posterior part of developing hindbrain or corresonding part of adult brain composed of medulla oblongata and lower part of 4th ventricle; regulates blood pressure, heart rate, and other involuntary functions

Question 5

Identify the ventricle of the brain.

Answer 5

-ventricles are fluid-filled cavities formed from the inner cavity of the neural tube
-2 lateral ventricles exist, one in each hemisphere, as well as a midline 3rd ventricle and a 4th ventricle in the hindbrain

Question 6

Describe the route of CSF circulation in the mammalian brain.

Answer 6

-ventricles and central canal of the spinal cord are connected
1. Choroid plexus
2. through lateral ventricles to 3rd ventricles and through aqueduct to 4th ventricle
3. subarachnoid space
4. drains through arachnoid villi to venous circulation

Question 7

Describe the function and composition of CSF.

Answer 7

-cerebral spinal fluid (CSF) is produced by specialized tissue found in each of the ventricles called the choroid plexuses
-CSF provides nourishment and provides protection as a shock absorber

Question 8

Identify the layers of the meninges.

Answer 8

Dura mater - outermost, tough connective tissue
Arachnoid - middle, delicate layer
Pia mater - innermost, direct contact with the brain

Question 9

Describe the anatomy and function of the dural venous sinuses.

Answer 9

-collecting pools of blood that drain CNS, face and scalp
-all dural venous sinuses ultimately drain into internal jugular vein
-don’t have valves
-spaces between the endosteal and meningeal layers of the dura
-are in between the periosteal and meningeal layers of the dura mater

Question 10

Define the cerebrum, sulci, gyri, nuclei, grey matter, white matter, cerebral hemispheres, longitudinal fissure, central sulcus, precentral gyrus, postcentral gyrus.

Answer 10

Cerebrum: structure formed from the telencephalon; largest portion of brain and is responsible for higher order mental functions
Sulci: depressed grooves of the convolutions of the cerebrum
Gyri: the elevated folds of the convolutions of the cerebrum
Nuclei: group of neuron bodies, often found within white matter
Gray Matter: marks the surface of the cerebrum; contains cell bodies
White Matter: found deeper in the cerebrum; consists of myelinated axons
Cerebral Hemispheres: cerebral cortex is divided into a right and left hemisphere that communicate with one another via the corpus callosum
Longitudinal Fissure: divides the left and right hemispheres
Central Sulcus: deep fissure/sulci that divides the frontal lobe from the parietal lobe
Precentral Gyrus: area involved in motor control located just in front of central sulcus
Postcentral Gyrus: area located just behind the central sulcus that contains the somatosensory cortex

Question 11

Identify the frontal, temporal, occipital, and parietal lobes of the cerebrum and discuss how each lobe contributes to maintaining homeostasis.

Answer 11

Frontal Lobe: anterior portion of each cerebral hemisphere until central sulcus
-responsible for voluntary motor control of skeletal muscle, personality, higher intellectual processes and verbal communication
Temporal Lobe: located below lateral sulcus
-responsible for interpretation of auditory sensations and memory
Occipital Lobe: located at the back of the brain
-responsible for integration of movements in focusing the eye, correlation of visual images with previous visual and other sensory stimuli, conscious perception of vision
Parietal Lobe: area behind the central sulcus
-responsible for somatesthetic interpretation, understanding speech and formulating words, and interpretation of textures and shapes

Question 12

Describe the basal nuclei and indicate its function.

Answer 12

Basal Nuclei: group of nuclei (gray matter) located deep within white matter of cerebrum
-AKA basal ganglia
-important for control of voluntary movement

Question 13

Discuss the limbic system in regards to emotions, memory, and olfaction.

Answer 13

-limbic system is a group of forebrain nuclei and fibre tracts including the cingulated gyris, the amygdala, the hippocampus and the septal nuclei
-cingulate gyrus and amygdala is also involved in emotions
-limbic system is also involved in the central processing of olfactory information

Question 14

Identify the basal nuclei and limbic system anatomically.

Answer 14

-basal nuclei include the corpus striatum, which is divided into the caudate nucleus, the putamen and the globus pallidus
-includes the subthalamic nucleus of the diencephalon and the substantia nigra of the midbrain
-limbic system includes the cingulated gyrus, amygdala, hippocampus and septal nuclei

Question 15

Identify the thalamus, hypothalamus, and posterior pituitary.

Answer 15

Thalamus: region of the diencephalon, accounting for 4/5 of it
Hypothalamus: medial, small region of the diencephalon lying below the thalamus
Pituitary: located immediately inferior to the hypothalamus

Question 16

Briefly describe the function of the thalamus.

Answer 16

-thalamus acts primarily as a relay centre through which all sensory information (except smell) passes on the way to the cerebrum
-key part of the accessory motor system along with the basal nuclei

Question 17

Describe, in detail, the functions of the hypothalamus.

Answer 17

Master Controller
-region contains neural centres for hunger and thirst, the regulation of body temperature, and hormone secretion from the pituitary
-contributes to the regulation of sleep, wakefulness, sexual arousal and performance, and such emotions are anger, fear, pain and pleasure
-body temperature is controlled through its ability to regulate the ANS
-pituitary gland secretions are controlled neuronal stimulation of the posterior pituitary or release of hormones from the hypothalamus to the anterior pituitary
-suprachiasmatic nuclei (SCN) are responsible for the control of circadian rhythms (sleep and wakefulness)

Question 18

Identify the mesencephalon and give its functions.

Answer 18

-mesencephalon (or midbrain) is located between the diencephalon and pons
-forms the upper part of the brain stem and contains the red nucleus (motor circuit) and the substantia nigra (motor circuit)
-also involved in visual/auditory reflexes

Question 19

Identify the pons and cerebrum and discuss their functions.

Answer 19

-pons and cerebellum are both regions of the metencephalon
-pons is anterior to the cerebellum and can be seen as a rounded bulge on the underside of the brain
-connects descending pathways from the cerebral cortex to the cerebellar cortex and medulla, and ascending tracts from the medulla to thalamus
-cerebellum is needed for motor learning and for coordinating the movement of different joints during movement, as well as the proper timing and force required for limb movements

Question 20

Discuss the medulla oblongata and indicate its vital functions that contribute to homeostasis.

Answer 20

-medulla oblongata is derived from the myelencephalon
-medulla is a conduit for ascending and descending nerve fibre tracts that connect the spinal cord to the rest of the brain
-medulla contains the ‘vital centres’, which are important for autonomic control of the heart and peripheral blood vessels, respiratory rate and depth and sneezing (along with centre in the pons), swallowing, coughing and vomiting reflexes

Question 21

Discuss the reticular activating system.

Answer 21

-reticular activating system (RAS) is an ascending arousal system
-RAS can filter out sensory information during sleep, but trigger consciousness when asleep or alertness if drowsy

Question 22

Differentiate between the spinal column and spinal cord.

Answer 22

Spinal cord is a continuation of the medulla. It is protected by the bony spinal column.

Question 23

Identify the cervical, thoracic, lumbar, sacral and coccygeal levels on the vertebral column and spinal cord.

Answer 23

Cervical: 7 vertebrae located in neck region, 8 nerves
Thoracic: 12 vertebrae located below the cervical spine through the thoracic cavity, 12 nerves
Lumbar: 5 vertebrae located below the thoracic spine in the lower region of the back; the spinal cord terminates at the level of the second lumbar vertebrae (conus medullaris), 5 nerves
Sacral: 5 fused vertebrae, located in pelvic region, 5 nerves
Coccygeal: 4 fused rudimentary vertebrae, 1 nerve

Question 24

Discuss the cauda equina and conus medullaris and its impact to medicine.

Answer 24

Cauda Equina: bundle of spinal nerves and spinal nerve roots; made of 2nd to 5th lumbar nerve pairs, 1st to 5th sacral nerve pairs and coccygeal nerve, all originate in conus medullaris of spinal cord
Conus Medullaris: due to differences in growth rate between spinal cord and vertebral column; spinal cord terminates at 2nd lumbar vertebrate named conus medullaris

Question 25

Discuss the anatomical arrangement of grey and white matter, dorsal and ventral roots, dorsal rot ganglia, central canal in the spinal cord.

Answer 25

-gray matter is located centrally and surrounded by white matter
-central gray matter shaped like an H; 2 dorsal (posterior) horns and 2 central (anterior horns)
-afferent nerves enter spinal cord branch into dorsal root
-efferent fibres that leave spinal cord leave by ventral root
-ventral and dorsal roots combine before leaving the vertebral column forming a peripheral spinal nerve
Dorsal Root Ganglion: enlargement of the dorsal root, and contains the cell bodies of sensory neurons
Central Canal: cavity of spinal column and is filled with CSF

Question 26

Identify the major tracts of the spinal cord and give their functions (spinocerebellar, spinothalamic, corticospinal, rubospinal, reticulospinal, vestibulospinal)

Answer 26

Spinocerebellar: ascending tract, starting in the spinal cord and terminating in the cerebellum
-conduct sensory impulses to cerebellum and necessary for coordinated muscle contractions
Spinothalamic: ascending tract, starting in spinal cord and terminating in thalamus, then cerebral cortex
-anterior tract conducts sensory impulses for crude touch and pressure
-posterior tract conducts pain and temperature impulses
Corticospinal: descending tract, originating in cerebral cortex
-primarily concerned with control of movements that require dexterity
Rubospinal: extrapyramidal-descending tract, originating in the red nucleus of the midbrain
-influences motor activity via information from cerebellum
Reticulospinal: an extrapyrimidal-descending tract, originating in reticular formation (medulla and pons)
-influences motor activity via information from cerebellum
Vestibulospinal: an extrapyrimidal-descending tract, originating in vestibular nuclei (medulla oblongata)
-influences motor activity via information from cerebellum

Question 27

Differentiate between an upper and lower motor neuron.

Answer 27

Upper Motor Neuron: somatic motor neurons with cell bodies in brain stem and spinal cord and axons that travel within nerves; to stimulate skeletal muscle contraction
-upper motor neurons are interneurons in the brain, contribute axons to descending motors tracts and influence lower motor neurons

Question 28

Describe how the dorsal and ventral roots combine to make a spinal nerve.

Answer 28

-each spinal nerves a mixed nerve made of sensory and motor fibres
-fibres are packaged together in nerve, but they separate near the attachment of nerve to spinal cord; produces 2 roots of each nerve
-dorsal = sensory, ventral = motor

Question 29

Identify the names and functions of the cranial nerves.

Answer 29

Cranial Nerves: sensory and motor neurons and somatic and autonomic neurons
In order from rostral to caudal: ‘o, o, o to touch and feel vaginas gets victor so hard’
1. Olfactory: sense of smell
2. Optic: vision
3. Oculomotor: eye movement, focus, amount of light that enters eye
4. Trochlear: eye movements
5. Trigeminal: somatic sensation from mouth, face, cornea, chewing
6. Abducens: eye movements
7. Facial: facial expression, taste sensation from anterior of tongue, lacrimal gland and salivary gland secretion
8. Vestibulocochlear: hearing and sense of balance
9. Glossopharyngeal: sensation from pharynx, taste sensation from posterior of tongue, carotid baroreceptors
10. Vagus: autonomic functions of gut and thorax, sensation of pharynx, muscle of vocal cords, swallowing reflex
11. Spinal Accessory: somatic innervation of shoulder and neck muscles
12. Hypoglossal: somatic innervations of tongue

Question 30

Describe the various reflex arcs and identify its components.

Answer 30

Reflex Arc: involuntary response to a stimulus, must have:
-sensory receptor to detect stimulus
-sensory neuron to transmit to spinal cord
-motor neuron to transmit involuntary impulses to an effector
-effector organ which will bring about response

Question 31

Define ipsilateral, contralateral, monosynaptic, polysynaptic, afferent, efferent, effector, interneuron, sensory receptor.

Answer 31

Ipsilateral: on the same side
Contralateral: taking place, or originating in the corresponding part of the opposite side of the body
Monosynaptic: type of reflex arc that is comprised of 2 neurons with one synapse separating the afferent and efferent arms of the reflex
Polysynaptic: type of reflex arc that involves multiple synaptic connections
Afferent: conveying or transmitting inward, towards a centre; afferent neurons conduct impulses towards the CNS
Efferent: conveying or transmitting something away from central location; efferent neurons conduct impulses away from the CNS
Interneuron: neurons within the CNS that don’t extend into the PNS; they are interposed between sensory and motor neurons
Sensory Receptor: receptor that when activated, send a signal via a sensory neuron

Question 32

Describe the knee-jerk, withdrawal and cross-extensor reflexes.

Answer 32

Knee-Jerk Reflex: strike right below the knee, and induce contraction of quadriceps muscle and a kick
-reflex is crucial for maintaining normal posture during standing, movement and locomotion
-Sensory Receptor: muscle spindle apparatus which detects stretch
-Effector: skeletal muscle
-localized to one side of the body and is termed ipsilateral reflex
Withdrawal Reflex: more complex reflex arcs of the body include the flexor reflex, which occurs in response to painful stimuli in limbs
-grabbing a hot pan leads to a painful stimuli that is sensed by naked dendrites of afferent neurons
-afferent signal is sent to the spinal cord via the dorsal root
-afferent neuron reaches the grey matter of the spinal cord it synapses on a interneuron
-interneuron integrates the sensory information and synapses on multiple efferent neurons that leave the spinal cord via the ventral roots
-one efferent signal stimulates flexor muscles and the other inhibits antagonistic extensor muscles that allow for quick and efficient withdrawal of the limb
Cross-Extensor Reflex: more complex withdrawal reflex occurs when you stand on a sharp object
-painful stimuli synapses on an interneuron (thus polysynaptic reflex arc) and sends out efferent signals to contract flexor leg muscles and relax extensor leg muscles
-may lead to loss of balance and falling
-cross-extensor reflex arc also crosses the midline of the body to mediate contraction of extensor muscles on the opposite limb to support the body’s weight

Question 33

Identify the peripheral nervous system.

Answer 33

PNS: consists of nerves that connects the CNS to all sensory receptors and effectors of the body

Question 34

Define somatic, autonomic, preganglionic, postganglionic, ganglion.

Answer 34

Somatic: motor neuron in the spinal cord that innervates skeletal muscle
Autonomic: division of nervous system that involves control of smooth muscle, cardiac muscle and glands (subdivided to PSNS and SNS)
Preganglionic: preganglionic neuron is the first neuron and synapses with the autonomic ganglion
Postganglionic: postganglionic neuron is the second neuron and synapses with the target tissue
Ganglion: collection of cell bodies outside the CNS

Question 35

Describe the anatomical arrangement of efferent neurons in the autonomic nervous system.

Answer 35

-efferent neurons of ANS involve a preganglionic neuron with its cell body located in CNS projecting to a ganglion
-preganglionic neuron synapses with postganglionic neuron
-postganglionic neuron is able to synapse with target tissue

Question 36

Indicate the anatomical locations of ganglia in the mammalian body.

Answer 36

-autonomic ganglia are locatde in the head, neck, and abdomen also parallel on each side of spinal cord
-location of autonomic ganglia helps to distinguish sympathetic and parasympathetic nervous systems

Question 37

Discuss the differences in the sympathetic VS parasympathetic nervous system in regards to: function, location of ganglia, neurotransmitters employed at chemical synapses, morphology and location of pre-ganglionic and post-ganglionic fibres.

Answer 37

Sympathetic Nervous System: prepares body for intense physical activity (fight or flight response)
-preganglionic fibres exit the spinal cord from the first thoracic (Tl) to the second lumbar (L2) levels
-post-synaptic neurons (para-vertebral ganglia) located on both side of the spinal cord
-sympathetic division, the ganglion cells are typically outside the target organ
-preganglionic fibre is cholinergic
-sympathetic postganglionic cells make norephinephrine
Parasympathetic Nervous System: relaxes the body, inhibits or slows down many high energy functions
-preganglionic fibres originate in the brain (midbrain, medulla oblongata, and pons) and in the 2nd to 4th sacral levels of the spinal column
-synapse in ganglia that are located next to or within the organs innervated ,called terminal ganglia (effector cells)
-preganglionic fibre is cholinergic
-parasympathetic postganglionic cells make acetylcholine

Question 38

Discuss the sympathetic nervous system and its contribution to homeostasis.

Answer 38

-mass activation of the sympathetic nervous system prepares the body for intense physical activity in emergencies; heart rate increases, blood glucose rises, and blood is diverted to skeletal muscles
-sympathetic nerves toniclly regulated the heart, blood vessels and other organs

Question 39

Describe the sympathetic chain and collateral ganglia of the sympathetic nervous system.

Answer 39

-many preganglionic fibres that exit the spinal cord below the diaphragm pass through the synaptic chain (of ganglia) without synapsing
-these preganglionic fibres form the splachnic nerve
-preganglionic fibres in the splanchnic nerves synapse in collateral, or prevertebral ganglia
-include the celiac, superior mesenteric, and inferior mesenteric ganglia
-postganglionic fibres that arise from the collateral ganglia innervate organs of the digestive, urinary, and reproductive system

Question 40

Discuss the function of the adrenal gland in regards to sympathetic responses.

Answer 40

-adrenal medulla (inner region of the adrenal gland) can be likened to a modified sympathetic ganglion
-cells of the adrenal medulla are innervated by preganglionic sympathetic fibres
-adrenal medulla secretes epinephrine into the blood stream in response to stimulation

Question 41

Describe the function of the vagus nerve in providing parasympathetic stimulation to viscera.

Answer 41

Vagus nerve provides the major parasympathetic innervation in the body; fibres are quite long and provide parasympathetic innervation to the heart, lungs, esophagus, stomach, pancreas, liver, small intestine, and upper half of the large intestine.

Question 42

Discuss the responses of various viscera to sympathetic and parasympathetic stimulation.

Answer 42

SNS: increase HR, vasoconstriction (skin), vasodilation (muscles), bronchodilation, relaxes GI walls, constricts sphincters, inhibits secretions, bladder relaxed, relaxation and contraction of uterus
PSNS: decrease HR, no affect, bronchoconstriction, contracts walls, relaxes sphincters, stimulates secretions, contracts bladder, no affect

Question 43

Identify receptors that provide adrenergic and cholinergic responses.

Answer 43

Adrenergic Responses:
-can have both excitatory and inhibitory responses
-alpha and beta-adrenergic receptors
-all adrenergic receptors act via G-proteins
-all beta-receptors produce their effects by stimulating the production of cyclic AMP within the target cells
-response of a target cell when norephinephrine binds to the α1 receptors is mediated by a different second-messenger system; rise in cytoplasmic concentration of Ca2+
-stimulation of α1 adrenergic receptors consistently causes contraction of smooth msucles
-stimulation of beta-adrenergic receptors promotes the relaxation of smooth muscles; but increases the force of contraction of cardiac muscle and promotes an increase in heart rate
Cholinergic Receptors:
-all somatic motor neuron, all preganglionic neurons (sympathetic and parasympathetic), and most post ganglionic parasympathetic neurons are cholinergic; they release ACh as a neurotransmitter
-somatic motor neurons and preganglionic autonomic neurons; always excitatory
-postganglionic parasympathetic axons are usually excitatory
-nicotinic and muscarinic cholinergic receptors
-5 different subtypes of muscarinic receptors (M1 through M5)
-some of these cause contraction of smooth muscles and secretion of glands, while others cause the inhibition that results in a slowing of the heart rate
-some (ex. M3) can cause an excitation (stimulating release of EDRF), which ultimately turns into an inhibitory effects (EDRF causes relaxation of arteriolar smooth muscle)