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Excitable Cells > 1. Gross structure of the nervous system > Flashcards

1. Gross structure of the nervous system Flashcards

1
Q

What are excitable cells? 2

A
  1. any cells transmitting/receiving electrical signals

2. includes microbes, plants and mammalian muscle cells and nervous system

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2
Q

Describe the nervous system of a primitive organism. 6

A
  1. eg. amoeba, hydra
  2. 500million years old
  3. input-output machine
  4. heat/light/food etc. reaches sensor
    1. Which goes to decision matrix, a stare machine that is not trainable or intelligent, and has a fixed response to a give output
  6. then to motor neurones, causing response
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3
Q

Describe the nervous system of a higher organism. 5

A
  1. sensor eg. eye goes to a pre-processor
  2. pre-processor simplifies complex info by:
    - judging data and data analysis
    - generating symbols
    - trainable - learning/memory
  3. then goes to decision matrix, then to controller
  4. controller assembles more complex outputs eg. all muscles needed for vision. can be trained
  5. then to motor response
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4
Q

describe invertebrate brains. 5

A
  1. analogous evolution of vertebrates and invertebrates
  2. sponges and jellies have a nerve net
  3. the invertebrate brain is the supraesophadeal ganglion
  4. Shared regions appear
  5. Vertebrates have a dorsal nerve cord and invertebrates have a ventral nerve cord
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5
Q

How did the vertebrate brain appear? 4

A
  1. amphioxus, a cephalochordate, has a small, central collection of neronal control
  2. its relative, the ragworm, has the start of a brain stem - 600M years old
  3. brain divisions common to all vertebrates include:
    - olfactory bulb
    - cerebral hemisphere
    - cerebellum
    - optic tectum
    - medulla oblongata
  4. mammals have a neocortex
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6
Q

Describe the mammalian nervous system.6

A
  1. the two structural divisions are the central nervous system (brain and spinal cord) and peripheral nervous system (sensory and motor nerves from spinal cord)
  2. PNS is split into 2 functional divisions
  3. somatic pns is under voluntary control and conscious perception
  4. it innervates and collects information from skin, muscles and joints
  5. autonomic pns (visceral) is not voluntary or concious
  6. innervates and collects information from smooth muscles incl blood vessels and glands
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7
Q

What is the autonomic nervous system? 4

A
  1. sympathetic is fight or flight
  2. controls activity that uses energy
  3. parasympathetic controls activities that conserve energy
  4. most parasympathetic nerves are cranial - stem from cranial vertebrae
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8
Q

Describe the spinal cord. 4

A
  1. Protected by spinal column and surrounded by three meninges which contain cerbrospinal fluid
  2. primary channel for messages from skin, joints and muscles to/from brain
  3. dorsal roots contain sensory, afferent neurons to the brain
  4. ventral roots contain motor, efferent neurons away from brain
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9
Q

What is the difference between white matter and grey matter in the brain? 2

A
  1. white matter is myelinated axons

2. grey matter is neuron cell bodies

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10
Q

What are the horns in the spinal cord? 4

A
  1. H shaped pattern of matter in spinal cord
  2. dorsal and ventral horns
  3. shape not wholly consistent through spine
  4. neurons go to upper and lower limbs so arrangement must reflect this
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11
Q

Describe the formation of the neural tube. 5

A
  1. ectoderm develops into nervous system, so ectoderm becomes develops into neural plate
  2. neural plate becomes nerual tube by folding and fusing
  3. walls of neural tube form cns
  4. neural crest becomes pns
  5. this should be complete in 22 days during human development
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12
Q

what is spina bifida? 5

A
  1. posterior of neural tube doesn’t close
  2. vertebrae fail to develop properly
  3. meninge seal forms and balloons out
  4. neurones grow into it and become damaged
  5. folic acid has a 90% success rate at preventing this
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13
Q

How do the different areas of the brain develop? 5

A
  1. 3 swellings at rostral end of neural tube, which become three primary vesicles
  2. prosencephalon/forebrain
  3. mesencephalon/midbrain
  4. rhombencephalon/hindbrain
  5. forebrain grows into two telencephalic vesicles, diencephalon and optic vesicles
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14
Q

What are ventricles in the brain? 2

A
  1. hollow and filled with cerebrospinal fluid

2. fluid formed in choroid plexus

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15
Q

Do you know the arrangement of the brain and spinal cord?

A

good effort

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16
Q

What is the brainstem? 5

A
  1. oldest and most primitive part of the brain
  2. contains decision matrix and controls vital functions
  3. contains midbrain - relay region
  4. midbrain is involved in movement, sensory input eg eyes and ears
  5. also contains hindbrain
17
Q

What is the hindbrain? 3

A
  1. Pons - switchboard which connects cerebellum to cerebral cortex
  2. Medulla - autonomic functions
  3. Cerebellum - not really a true part of the hindbrain, sticks out behind it
18
Q

Describe the pons and medulla. 4

A
  1. pons swells out from ventral surface of brain stem
  2. contains many cell bodies
  3. important relay between cortex and cerebellum
  4. medulla is important in control of bp and respiration
19
Q

What is the impact of brain stem damage? 4

A
  1. hydrocephalus (liquid on brain) and haemorrhage increases pressure in the head
  2. fluid can’t escape from fused skull
  3. severe cases can lead to coning of stem
  4. damage to medulla leads to respiratory arrest
20
Q

What is decussation. 4

A
  1. crossing over of neurons in medullary pyramids
  2. corticospinal tract crosses over in medulla
  3. right hemisphere controls left body
  4. left hemisphere controls right body
21
Q

What is the cerebellum? 5

A
  1. old/primitive brain part
  2. movement control centre incl fine movement
  3. extensive connections to cerebrum and spinal cord - 2x more neurons than both cerebral hemispheres
  4. diseases incl ataxias - aberrant movement coordination
  5. one 24year old survived this long without one!
22
Q

what are the diencephalon and the mesencephalon? 5

A
  1. midbrian has linkagesbetween components of motor systems eg. substantia nigra
  2. substantia nigra is damages in parkinson’s
  3. diencephalon contains thalamus and hyopthalamus
  4. thalamus - relay and gating roles
  5. hypothalamus - homeostasis and reproduction
23
Q

What is the cerebral cortex? 5

A
  1. clear division between halves along sagittal fissure
  2. Controls:
    - voluntary actions
    - cognition
    - perception/awareness
  3. mammals have a more complex, 6 layered (vs 1) neocortex
  4. allows more nerves so more intelligence
  5. different sizes but same general structure
24
Q

What is cortical folding? 6

A
  1. more processing power needed for more intelligence
  2. cortical neurones represent processing power
  3. skull is a confined structure so volume and mass should be kept to a minimum
  4. big heads are more difficult to protect
  5. sheet of cortex folds into gyrus (peak) and sulcus (trough)
  6. central sulcus goes laterally-medially
25
Q

Describe the lobes of the cerebral cortex.3

A
  1. different parts have different functions
  2. pre-central gyrus - motor and post-central gyrus - sensory
  3. cortical lobes clockwise from rostral:
    - – frontal
    - parietal
    - occipital
    - temporal
26
Q

What is the homunculus? 3

A
  1. shows location and amount of neocortex dedicated to particular function
  2. proportional to neuronal composition, not body part mass
  3. inhumans, shows importance of finger movements and speech control
27
Q

What are Electroencephalograms (EEG)? 6

A
  1. electrodes placed on skull
  2. brainwaves measured corresponding to activity
  3. different patterns associated with different things
  4. epilepsy - random peaks across all
  5. bleeding - global calming of waves
  6. fast and cheap but difficult to interpret and poor resolution
28
Q

What is a CT scan? 3

A
  1. shows large structures and problems
  2. uses harmful x-ray radiation
  3. only shows one plane
29
Q

what is magnetic resonance imaging (mri)? 6

A
  1. strong magnetic field and radiowaves
  2. higher resolution
  3. electromagnetic radiation causes protons to switch between increased and decreased energy frequencies, which releases more EMR
  4. the more detected, the more fluid there is
  5. covers whole brain without harm
  6. useful for soft tissues and very expensive
30
Q

What is a PET scan? 3

A
  1. injection of radioactive glucose
  2. differential take up depending on brain activity
  3. hihglights increased brain activity from positron emissions
31
Q

What is an fMRI? 1

A
  1. Oxyhaemoglobin has a different magnetic resonance to deoxyhaemoglobin

Excitable Cells (8 decks)

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