CNS-sensory/Motor

Question 1

Major Divisions of the nervous system

Answer 1

• Afferent (sensory input) : cell bodies out of CNS
• Cranial Nerves: somatic, visual, olfactory, taste, auditory
• Spinal Nerves: Somatic Sensation Touch, Temperature, Pain
• Efferent(motor output): cell bodies in CNS
• Cranial Nerves
• Spinal Nerves
• Somatic Efferent: Innervates skeletal muscle, only excitatory (ACh), Motor Neurons
• Autonomic efferent: innvervates interneurons, Smooth and cardiac muscle, Excitatory and inhibitory.
• Enteric

Question 2

Brain Anatomy

Answer 2

• Cerebrum (cortex) : frontal, central sulcus, parietal, lateral sulcus, occipital temporal
• Corpus Callosum
• Thalamus
• Brainstem: midbrain, pons, medulla
• Cerebellum

Question 3

Divisions of the Spinal Cord

Answer 3

-Cervical nerves (8 pair): neck, shoulders, arms, and hands
-Thoracic Nerves(12 pairs): shoulders, chest, upper abdominal wall
-Lumbar nerves(5 pairs): lower abdominal wall, hips, and legs
Sacral Nerves (5 pairs): genitals and lower digestive track
-Coccygeal nerves (1 pair)

Question 4

Early development of the Nervous system

Answer 4

Fertilized egg (ovum) –> ball of cells –> Blastocyst (week 1) –> Blastocyst (week 2) –> Blastocyst (week 3) : inside is the embryonic disk + neural plate

Question 5

The neural tube

Answer 5

• vesicles develop during week 4
• forebrain
• midbrain
• hindbrain

Question 6

The forebrain becomes?

Answer 6

Cerebral hemispheres + thalamus

Question 7

The midbrain becomes?

Answer 7

Midbrain

Question 8

The hindbrain becomes?

Answer 8

Cerebellum: pons + medulla

Question 9

Ventricles

Answer 9

• space between the tissues of the brain.

- contain 150 mL of cerebral spinal fluid

Question 10

Formation of cerebrospinal Fluid

Answer 10

-produced by the choroid plexus ( in the four ventricles, but mainly the two lateral) at a rate of 500 mL/day

Question 11

Function of cerebrospinal Fluid

Answer 11

1. Supports and cushions the CNS. Specific gravity of CSF and the brain are equal
2. Provides nourishment to the brain
3. Removes metabolic waste trhough absorption at the arachnoid villi.

Question 12

Composition of cerebrospinal Fluid

Answer 12

-sterile, colorless, acellular fluid that contains glucose

Question 13

Circulation of cerebrospinal Fluid

Answer 13

-passive (not pumped)

Question 14

3 meninges(membranes) of the CNS

Answer 14

• cover the brain and spinal chord

-

Question 15

How does the CSF returned to the blood

Answer 15

returns via the dural sinus

Question 16

Characteristics about the blood supply to the brain

Answer 16

• glucose is usually the only substrate metabolized by the brain
• very little glycogen in the brain
• Brain needs a continous supply of glucose and oxygen (glucose transport into the brain does not require insulin)
• A few seconds of blood supply interruption can lead to loss of consciousness. A few minutes can lead to neuronal death (stroke)
• Brain receives 15% of total blood (but 2% of total mass)

Question 17

Path of blood from the heart to the brain

Answer 17

heart –> Aorta –> either brain or body (85%) –> Vertebral or Common carotid artery –> Internal Carotid Artery (base of the brain) or External Carotid Artery (outside of the head).

Question 18

Path of Cerebral Circulation: CSF and blood

Answer 18

CSF –> Choroid Plexus –> ventricles –> subarachnoid space –> arachnoid villi –> dural sinus –> venous system –> heart –> Carotid Arteries or Vertebral arteries –> circle of willis –> brain –>Venous –> heart.

Question 19

Blood-brain barrier (capillary wall)

Answer 19

• tight junctions between endothelial cells
• impermeable to plasma proteins and large organic molecuels
• permeable to Water, CO2, O2, Lipid-soluble substances, Na+, K+, Cl -
• active transport of glucose and some amino acids

Question 20

Senesation

Answer 20

awareness of sensory stimulation

Question 21

perception

Answer 21

the understanding of a sensations meaning

Question 22

Law of specific nerve energies

Answer 22

regardless of how a sensory receptor is activated, the sensation felt corresponds to that of which the receptor is specialized

Question 23

Law of projection

Answer 23

regardless of where in the brain you stimulate a sensory pathway, the sensation is always felt at the sensory receptors location

Question 24

Modality

Answer 24

General class of a stimulus

Question 25

Labeled-line

Answer 25

the brain “knows” the modality and location of every sensory afferent

Question 26

How Sensory Receptors work

Answer 26

1. Stimulus energy –> adequate stimulus(specificity)
2. Receptor membrane
3. transduction
4. Ion channel activation
5. Afferent (signal sent to brain)

Question 27

Acuity

Answer 27

ability to differentiate one stimulus from another

Question 28

Receptive field (RF)

Answer 28

The region in space that activates a sensory receptor or neuron

Question 29

Lateral inhibition

Answer 29

• 2 order neurons send signal via interneurons to decrease the intensity of a stimulus.
• helps localize a stimulus

Question 30

Touch: Mechanoreceptors:

Answer 30

specialized end organs that surround the nerve terminal. These organs allow only selective mechanical information to activate the nerve terminal

Question 31

Superficial Layers

Answer 31

Meissner’s Corpuscle: fluid-filled strucutre enclosing the nerve terminal, Rapidly adapting. Light stroking and fluttering

Merkel Disk: small epithelial cells surround the nerve terminal. Slowly adapting, pressure and texture

Question 32

Deep Layers

Answer 32

Pacinian Corpuscle: Large capsules of connective tissue surround the nerve terminal. Rapidly adapting, strong vibrations

Ruffini endings: Nerve endings wrap around a spindle-like structure. Slowly adapting, stretch and bending of skin.

Question 33

proprioception

Answer 33

muscle spindles provide sense of static position and movements of limbs and body

Question 34

How are mechanoreceptors activated

Answer 34

by stretching the cytoskeletal strands.