Topic 19 -Nervous system brain and spinal cord Flashcards
Forebrain
cerebrum
Diencephalon
Cerebrum
lobes
(= right and left cerebral hemispheres)
i) frontal
ii) temporal
iii) parietal
iv) occipital
v) insula – deep to temporal lobe
Cerebrum surface features
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
cerebrum 3 layers
cerebral cortex
tracts
basal nuclei
cerebrum: cerebral cortex
- 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
cerebrum: tracts (white matter)
- 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)
cerebrum: basal nuclei
- paired masses of gray matter (within the white matter)
- involved in control of skeletal muscle movement
Diencephalon
- 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
Midbrain
anterior portion=
Posterior portion=
- 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
Hindbrain
pons
medulla oblongata
cerebellum
hindbrain: pons
- anterior to cerebellum
- contains
- tracts between brain + spinal cord + tracts to/from cerebellum
- pontine respiratory centres
hindbrain: medulla oblongata
What are the 2 bulges
What are the three vital centres
- 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
Brain stem=
midbrain, pons and medulla
hindbrain: cerebellum
- 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
Functional systems in brain
Limbic system
Reticular formation
Limbic system
- nuclei in cerebrum + diencephalon
- regulates emotions + emotional behaviours (laughing, crying etc)
- contains areas involved in memory (memories evoke emotional responses)
Reticular formation
- 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
Spinal cord overview
- 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
Cross section of spinal cord
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
functions of spinal cord
- carries sensory and motor impulses
- produces reflexes
- fast, predictable, automatic responses to changes in the environment
e. g. withdrawal reflex
