Topic 19 -Nervous system brain and spinal cord

Question 1

Forebrain

Answer 1

cerebrum

Diencephalon

Question 2

Cerebrum

lobes

Answer 2

(= right and left cerebral hemispheres)

i) frontal
ii) temporal
iii) parietal
iv) occipital
v) insula – deep to temporal lobe

Question 3

Cerebrum surface features

Answer 3

i) fissures = deep grooves
① longitudinal fissure - separates right and left hemispheres
② transverse fissure - separates cerebellum + cerebrum
③ lateral fissure – separates temporal lobe from rest of cerebrum
ii) gyri = ridges
- examples:
- postcentral gyrus in parietal lobe
- precentral gyrus in frontal lobe
iii) sulci = shallow grooves (separate gyri)
- example:
- central sulcus – between frontal and parietal lobes

Question 4

cerebrum 3 layers

Answer 4

cerebral cortex
tracts
basal nuclei

Question 5

cerebrum: cerebral cortex

Answer 5

• 2-4 mm thick, gray matter
• has functional areas:
  ① motor areas
• all in frontal lobe
• control skeletal muscle movement
• 3 regions:
  a) primary motor area (precentral gyrus)
  b) premotor area
  c) Broca’s – language
  ② sensory areas
  a) general sensory area (pain, temp, touch, pressure)
• postcentral gyrus in parietal lobe
  b) vision – occipital lobe
  c) auditory + olfaction - temporal lobe
  d) taste + visceral sensation (e.g. full bladder) - insula
  ③ association areas - recognize info from memories
• parietal, occipital, temporal lobes
  ④ others
• memory - temporal lobes
• conscious intellect (personality, learning, ideas, judgement etc) - prefrontal cortex

Question 6

cerebrum: tracts (white matter)

Answer 6

• types:
  ① association tracts
• from gyrus to gyrus in same hemisphere
  ② commissural tracts
• from gyrus to gyrus in opposite hemispheres
• e.g. corpus callosum
  ③ projection tracts - run vertically (brain to spinal cord / spinal cord to brain)

Question 7

cerebrum: basal nuclei

Answer 7

• paired masses of gray matter (within the white matter)

- involved in control of skeletal muscle movement

Question 8

Diencephalon

Answer 8

• all gray matter
  i) thalamus - 2 lobes connected by intermediate mass (bridge of gray matter across 3rd ventricle)
• relay station for most sensory impulses to cortex
  ii) hypothalamus
• inferior to thalamus, above pituitary
• major regulator of the internal environment (visceral control)
  e. g. blood pressure, heart rate

Question 9

Midbrain

anterior portion=

Posterior portion=

Answer 9

• connects pons + diencephalon
• contains cerebral aqueduct
• anterior portion = cerebral peduncles (projection tracts)
• posterior portion = 4 nuclei = corpora quadrigemina
• 2 superior colliculi
• visual reflexes
• 2 inferior colliculi
• hearing + auditory reflexes

Question 10

Hindbrain

Answer 10

pons
medulla oblongata
cerebellum

Question 11

hindbrain: pons

Answer 11

• anterior to cerebellum
• contains
• tracts between brain + spinal cord + tracts to/from cerebellum
• pontine respiratory centres

Question 12

hindbrain: medulla oblongata

What are the 2 bulges

What are the three vital centres

Answer 12

• inferior to pons
• ends at foramen magnum
• 2 bulges called pyramids = large motor tracts (= part of corticospinal tracts)
• just above spinal cord ⇒ decussation of pyramids (tracts cross over)
• 3 vital centres (nuclei) in medulla:
  i) cardiac
  ii) vasomotor (blood vessels)
  iii) respiratory
• several non-vital centres - for swallowing, sneezing, vomiting

Question 13

Brain stem=

Answer 13

midbrain, pons and medulla

Question 14

hindbrain: cerebellum

Answer 14

• posterior to pons, medulla
• has folds similar to gyri = folia
• cortex (gray matter)
• arbor vitae (deep to cortex, anterior cerebellum) = white matter
• coordinates skeletal muscle contraction
• posture, balance

Question 15

Functional systems in brain

Answer 15

Limbic system

Reticular formation

Question 16

Limbic system

Answer 16

• nuclei in cerebrum + diencephalon
• regulates emotions + emotional behaviours (laughing, crying etc)
• contains areas involved in memory (memories evoke emotional responses)

Question 17

Reticular formation

Answer 17

• nuclei in brain stem
• cortex, thalamus + hypothalamus involved
• together form RAS = Reticular Activating System
• regulates alertness + attention
• filters stimuli + only sends new/unusual signals to other brain areas
• sleep results when inhibited
• if damaged = coma

Question 18

Spinal cord overview

Answer 18

• foramen magnum to level of lumbar vertebrae L1/L2 (conus medullaris)
• nerves continue down from spinal cord through vertebral foramina as cauda equina (“horse’s tail”)
• exit at intervertebral foramina
• filum terminale
• CT = extension of pia mater - anchors conus medullaris of spinal cord to coccyx
• location where CSF samples taken

Question 19

Cross section of spinal cord

Answer 19

a) anterior median fissure + posterior median sulcus
Separate cord into right and left halves
b) central canal – contains CSF
c) gray matter - cell bodies + dendrites of motor neurons, interneurons 
- H-shaped
- cross bar = gray commissure
- horns
i) dorsal horn = sensory
ii) lateral horn = motor
iii) ventral horn = motor	
d) White matter
- myelinated axons = ascending (sensory) and descending (motor) tracts
- forms columns:
i) dorsal column
ii) lateral column
iii) ventral column

Question 20

functions of spinal cord

Answer 20

• carries sensory and motor impulses
• produces reflexes
• fast, predictable, automatic responses to changes in the environment
  e. g. withdrawal reflex