The Nervous System

Front 1

Give a definition of "Nervous System"

Back 1

A collection of tissues and their cell processes (nerves) that collect info from external/internal environment, analyze and store info, and provide appropriate responses that promote survival of the organism

Front 2

How is the CNS protected?

Back 2

1. Brain and spinal cord = within cranium and spinal canal and covered by 3 sheets of tissue (meninges)
2. tight juctions b/w endothelial cells of blood vessels in brain form blood-brain barrier
3.Cerebrospinal fluid within the ventricles of the brain that flows down to brainstem and exits to bathe the external surface of the brain

Front 3

What is the "Blood-Brain Barrier"

Back 3

-Tight juctions that seal together endothelial cells of brain capillaries
-thick basement membrane around the caps

Front 4

What structure is responsible for the production of cerebrospinal fluid

Back 4

-choroid plexus = networks of capillaries in walls of ventricles
-caps covered by ependymal cells that form CSF from blood plasma by filtration and secretion

Front 5

How does the CSF protect the brain?

Back 5

-Protects brain from mechanical shock
-Draws away metabolic breakdown products (waste)

Front 6

How much CSF flows and is resorbed?

Back 6

480ml per day

Front 7

What is the function of the blood CSF barrier?

Back 7

-Prevents passive diffusion of solutes from blood into the CSF

Front 8

Where is the CSF absorbed?

Back 8

-CSF absorbed into venous blood through the arachnoid granulations
-arachnoid granulations protrude from thin 2nd covering of brain (arachnoid) and extend to venous sinus of brain, allowing CSF to exit into bloodstream

Front 9

What makes up the central nervous system?

Back 9

brain + spinal cord

Front 10

What makes up the peripheral nervous system?

Back 10

1.nerves (and ganglia) carrying info from limbs (afferent)
2.nerves carrying info to muscles to control movement (efferent)
3.nerves + ganglia of autonomic NS
4.nerves + ganglia of enteric NS controling gut function

Front 11

Where does the spinal cord lie, and how/what is it connected to?

Back 11

-Spinal cord lies within spinal canal of the vertebral column (spine)
-spinal cord is connected by nerves to limbs and torso

Front 12

What types of tissue are contained in the spinal cord

Back 12

1.White matter = forms external part of cord (myelinated axons, thus white)
2.Gray matter = forms butterfly shaped inner core (neuron cell bodies, dentrites, synapses)

Front 13

In which type of matter (white or gray) does axonal conduction take place in?

Back 13

White matter (contains axons carrying info up and down axis of spinal cord)

Front 14

In which type of matter (white or gray) does neurotransmission take place in?

Back 14

Gray matter

Front 15

How do action potentials (info) enter the spinal cord?

Back 15

via spinal nerves

Front 16

How many nerves are there per spinal vertebra?

Back 16

one pair

Front 17

What are spinal nerves?

Back 17

-Mixed nerves carrying sensory info to the spinal cord and motor information from the spinal cord to muscle nerves

Front 18

What do nerves from lower regions (caudal end, lumbar region) of spinal cord innervate?

Back 18

Lower limbs

Front 19

What do nerves in mid regions (thoracic regions) of spinal cord innervate?

Back 19

chest + abdomen

Front 20

What do nerves of upper part (cervical) of spinal cord innervate?

Back 20

upper limbs

Front 21

What requires more sensory and motor axons, chest + abdomen OR lower + upper limbs

Back 21

-Upper and lower limbs require more sensory and motor axons
(For this reason, spinal cord is larger in lumbar and cervical regions than thoracic region = cervical + lumbar enlargements)

Front 22

What is longer, the vertebral column or the spinal cord?

Back 22

-Vertebral column is longer; spinal cord ends @ L1 and the lumbar nerves descend within a CSF filled sac

Front 23

What makes up the CSF filled sac?

Back 23

Meninges = the layer of membrane covering the brain and spinal cord form walls of sack and trap the fluid

Front 24

What is the lumbar cistern?

Back 24

-Fluid space caudal to end of spinal cord
(point that CSF can be sampled using lumbar puncture = spinal tap)

Front 25

What do the nerves split into when they reach the spinal cord?

Back 25

dorsal (posterior) root + ventral (anterior) root

Front 26

What does the dorsal root contain?

Back 26

sensory axons of the mixed nerve

Front 27

What does the ventral root contain

Back 27

motor axons of the mixed nerve

Front 28

Where does the dorsal root connect to the spinal cord?

Back 28

At the dorsal horn of the gray matter

Front 29

What is the dorsal horn of the grey matter and what does it contain?

Back 29

Dorsal horn = sensory part of the gray matter of the spinal cord
-Contains synaptic terminals of some sensory axons of the nerve and cell bodies and dentdrites of the neurons that will send projections to the brain

Front 30

What is the ventral horn and what does it contain?

Back 30

Ventral horn= motor part of the spinal gray matter
-Contains cell bodies of motor neurons which will innervate muscle and activate neuromuscular junction to cause muscle contraction

Front 31

Explain the withdrawal reflex.

Back 31

-touch hot object, pain fibers (axon) send series of APs to dorsal horn of spinal cord
-nerve terminal of these axons contact dendrites of motor neurons; motor neurons innervate muscle gr. causing arm to flex from source

Front 32

Where do the axons contained in the white matter project to?

Back 32

From the spinal cord to the brain
From the brain to the spinal cord

Front 33

What are tracts?

Back 33

Bundle of axons w a similar function (starting pt and end pt)

Front 34

What is the corticospinal tract

Back 34

-Important descending tract found in lateral white matter
-carries the axons of neurons in the cerebral cortex that project down to the spinal cord
-Innervate ventral horn to control movement

Front 35

What is the dorsal column and what does it contain?

Back 35

-White matter found in between the two dorsal horns
-Contains axons of sensory neurons that DONT synapse in the dorsal horn but instead project to brain stem to synapse

Front 36

what is the foramen magnum and what happens @ this structure?

Back 36

-foramen magnum = big hole @ base of skull
-spinal cord merges w caudal part of brain stem

Front 37

Whats parts is the brain composed of?

Back 37

1)Brainstem
2)Cerebellum
3)Diencephalon
4)Cerebrum

Front 38

What is the conscious decision-making part of the brain?

Back 38

Cerebrum

Front 39

What is the gateway for sensory information in the brain?

Back 39

Diencephalon

Front 40

What part of the brain exerts fine control over motor function?

Back 40

Cerebellum

Front 41

What part of the brain carries info to and from sipinal cord and also controls motor and sensory function of head + neck?

Back 41

brains stem

Front 42

How does the brainstem connect to the spinal cord and to the diencephalon?

Back 42

-brainstem connects to the spinal cord @ its caudal end (tail)
-brainstem connects to diencephalon @ its rostral end (beak)

Front 43

What does the brainstem consist of ?

Back 43

1. Medulla Oblongada (caudal)
2. Pons (middle)
3. Midbrain (rostral)

Front 44

What is superior to the brainstem? What is posterior?

Back 44

Superior = Diencephalon
Posterior = Cerebellum

Front 45

What does the diencephalon consist of?

Back 45

1. Thalamus
2. Hypothalamus
3. Epithalamus

Front 46

What structure is supported on the diencephalon?

Back 46

Cerebrum

Front 47

What is the purpose of the BBB?

Back 47

-blood brain barrier protects brain cells from harmful substances and pathogens
-prevents passage of many substances from blood into brain tissue

Front 48

Name a few substances which cross the BBB by active transport.

Back 48

-a few water soluble substances ex. glucose

Front 49

Name a few substances with cross the BBB very slowly.

Back 49

-Urea, creatinine, most ions

Front 50

Which substances do not cross the BBB (from blood to brain tissue) at all?

Back 50

-proteins and most antibiotic drugs

Front 51

What substances easily cross the blood-brain barrier?

Back 51

Lipid soluble substances such as oxygen, carbon dioxide, alcohol, most anesthetic agents

Front 52

How does the cerebral spinal fluid contribute to homeostasis?

Back 52

1. Mechanical protection (shock absorbing medium)
2. Chemical protection (provides optimal chemical env for neuron siganaling)
3. Circulation (allows exhange of nutrients & waste b/w blood and nervous tissue)

Front 53

How is the blood-cerebrospinal barrier formed?

Back 53

-Ependymal cells covering caps of choroid plexuses are joined by tight juctions
-Thus, materials entering CSF from choroid caps cannot leak b/w these cells
-Must pass through ependymal cells

Front 54

Name a few structures contained in the brainstem spinal cord

Back 54

1. Inputs and outputs (cranial nerves)
2. ascending and descending axon tracts that pass through it
3. Collection of neurons (or nerve cell bodies) that process info and perform functions

Front 55

What tracts are found in the medulla?

Back 55

-Ascending tracts like the dorsal columns (sensory)form synapses in medulla
-Descending tracts like the corticospinal tract (motor)

Front 56

What are some of the functions performed by neurons found in the medulla?

Back 56

-control of breathing and vomitting

Front 57

What are the inputs/outputs found in the medula?

Back 57

-Cranial Nerves

Front 58

Compare spinal and cranial nerves.

Back 58

-Spinal nerves carry sensory & motor info from sacrum and coccyx to the level of the neck (upper cervical nerves)
-Above this level, in region of head and face, nerves enter the cranium rather than spinal cord = cranial nerves

Front 59

How many cranial nerves are there?

Back 59

12 pairs

Front 60

What are pyramids?

Back 60

-Part of medulla; bulges formed by large corticospinal tracts that pass from cerebrum to spinal cord

Front 61

What is the "decussation of pyramids" and what are its implications?

Back 61

-90% of axons in left pyramid cross to right side (vice versa)
-Cortex on right side of brain send and receives info from left side of body (vice versa)

Front 62

What happens @ the dorsal column nuclei?

Back 62

-Sensory axons that do not synapse in the spinal cord dorsal horn ascend the spinal cord in the dorsal column nuclei and synapse there, in the medulla

Front 63

What are cranial nerve nuclei?

Back 63

-Are nuclei (collection of cell bodies) that receive sensory info from cranial nerves
-OR are collections of motor neurons that send out info to muscles of the head and face

Front 64

What are the pons?

Back 64

Bridge that connects parts of the brain with one another (medulla + midbrain)

Front 65

What kind of structures are contained in the pons?

Back 65

-Inputs and outputs (some cranial nerves)
-ascending and descending axon tracts passing through it
-collection of neurons (or nerve cell bodies)

Front 66

What structure is the upper part of the brainstem?

Back 66

Midbrain

Front 67

What structures are contained in the midbrain?

Back 67

-Inputs and outputs (some cranial nerves)
-Ascending and descending axon tracts passing through it (some which form synaptic terminals
-Collection of neurons (or nerve cell bodies) that process info and perform functions

Front 68

What are some of the notable anatomical structures in the midbrain?

Back 68

1. Cerebral peduncles
2. Medial lemniscus
3. Superior (and inferior) colliculus
4. Substantia nigra

Front 69

What are the cerebral peduncles?

Back 69

-pair of tracts
-contain descending corticospinal fibers (conduct nerve impulses from cerebrum to spinal cord)

Front 70

What is the medial lemniscus?

Back 70

-large bundle of heavily myelinated ascending sensory fibers

Front 71

What is are superior colliculi?

Back 71

-serve as reflex centers for some visual activities

Front 72

What are the inferior colliculi

Back 72

-part of the auditory pathway
-relay impulses from the receptors for hearing in the ears to the thalamus

Front 73

What is the substantia nigra?

Back 73

-very important nuclei for motor control

Front 74

What are the 2 parts of the diencephalon?

Back 74

1. Thalamus
2. Hypothalamus

Front 75

In a sentence, describe the role of the thalamus.

Back 75

-Thalamus = part of the brain that recieves synapses from all ascending sensory innervation and sends projection to the appropriate part of the cerebral cortex

Front 76

The thalamus is said the be the gateway to the cortex for all sensations except for one. Which one?

Back 76

smells

Front 77

How many cranial nerves enter @ the level of the diencephalon? Name them.

Back 77

-Only one cranial nerve enters @ level of diencephalon = optic nerve carrying visual sensory info

Front 78

What is the role of the hypothalamus?

Back 78

-Hypotalamus = high command center for homeostasis within the brain
-Controls BP, body temp, blood glucose, and other housekeeping functions

Front 79

Where do ascending and descending info within the diencephalon travel?

Back 79

-In axon tracts within the internal capsule

Front 80

What 2 structures compose the cerebrum?

Back 80

1. Cerebral cortex
2. Basal Ganglia

Front 81

What is the cerebral cortex?

Back 81

-Outer coating of "brain"
-Gray matter of cerebral cortex is outside, white matter inside (inverse of spinal cord)

Front 82

Describe the spacial arrangement of the cortex

Back 82

-Cortex is convoluted into ridges called gyri and folds called sulci

Front 83

Why is the cortex convoluted?

Back 83

To increase surface area in a small space

Front 84

What are the main roles of the cerebral cortex?

Back 84

-Cortex receives and perceives sensory input

Front 85

How does the cerebral cortex make sense of the sensory input received?

Back 85

-Relative to past experience (memory and sends out appropriate response commands)

Front 86

What are lobes?

Back 86

Territories into which is organised the cerebral cortex

Front 87

How many lobes are found in the cerebral cortex and what are they?

Back 87

- 4 lobes
1. Frontal lobe
2. Parietal lobe
3. Occipital lobe
4. Temperal lobe

Front 88

What is the frontal lobe?

Back 88

-Site of motor commands that are sent out to the brainstem and spinal cord

Front 89

What is the parietal lobe?

Back 89

-Site of receipt of sensory info for pain, temperature, touch and pressure

Front 90

What is the occipital lobe?

Back 90

-Site of receipt of visual information

Front 91

What is the temperal lobe?

Back 91

-Site of receipt of auditory info

Front 92

Briefly, what is the basal ganglia?

Back 92

-Part of cerebrum lying deep to the cortex and its underlying white matter
-Large collections of neuronal cell bodies that are important in motor function