1. Gross structure of the nervous system Flashcards
1
Q
What are excitable cells? 2
A
- any cells transmitting/receiving electrical signals
2. includes microbes, plants and mammalian muscle cells and nervous system
2
Q
Describe the nervous system of a primitive organism. 6
A
- eg. amoeba, hydra
- 500million years old
- input-output machine
- heat/light/food etc. reaches sensor
- Which goes to decision matrix, a stare machine that is not trainable or intelligent, and has a fixed response to a give output
- then to motor neurones, causing response
3
Q
Describe the nervous system of a higher organism. 5
A
- sensor eg. eye goes to a pre-processor
- pre-processor simplifies complex info by:
- judging data and data analysis
- generating symbols
- trainable - learning/memory - then goes to decision matrix, then to controller
- controller assembles more complex outputs eg. all muscles needed for vision. can be trained
- then to motor response
4
Q
describe invertebrate brains. 5
A
- analogous evolution of vertebrates and invertebrates
- sponges and jellies have a nerve net
- the invertebrate brain is the supraesophadeal ganglion
- Shared regions appear
- Vertebrates have a dorsal nerve cord and invertebrates have a ventral nerve cord
5
Q
How did the vertebrate brain appear? 4
A
- amphioxus, a cephalochordate, has a small, central collection of neronal control
- its relative, the ragworm, has the start of a brain stem - 600M years old
- brain divisions common to all vertebrates include:
- olfactory bulb
- cerebral hemisphere
- cerebellum
- optic tectum
- medulla oblongata - mammals have a neocortex
6
Q
Describe the mammalian nervous system.6
A
- the two structural divisions are the central nervous system (brain and spinal cord) and peripheral nervous system (sensory and motor nerves from spinal cord)
- PNS is split into 2 functional divisions
- somatic pns is under voluntary control and conscious perception
- it innervates and collects information from skin, muscles and joints
- autonomic pns (visceral) is not voluntary or concious
- innervates and collects information from smooth muscles incl blood vessels and glands
7
Q
What is the autonomic nervous system? 4
A
- sympathetic is fight or flight
- controls activity that uses energy
- parasympathetic controls activities that conserve energy
- most parasympathetic nerves are cranial - stem from cranial vertebrae
8
Q
Describe the spinal cord. 4
A
- Protected by spinal column and surrounded by three meninges which contain cerbrospinal fluid
- primary channel for messages from skin, joints and muscles to/from brain
- dorsal roots contain sensory, afferent neurons to the brain
- ventral roots contain motor, efferent neurons away from brain
9
Q
What is the difference between white matter and grey matter in the brain? 2
A
- white matter is myelinated axons
2. grey matter is neuron cell bodies
10
Q
What are the horns in the spinal cord? 4
A
- H shaped pattern of matter in spinal cord
- dorsal and ventral horns
- shape not wholly consistent through spine
- neurons go to upper and lower limbs so arrangement must reflect this
11
Q
Describe the formation of the neural tube. 5
A
- ectoderm develops into nervous system, so ectoderm becomes develops into neural plate
- neural plate becomes nerual tube by folding and fusing
- walls of neural tube form cns
- neural crest becomes pns
- this should be complete in 22 days during human development
12
Q
what is spina bifida? 5
A
- posterior of neural tube doesn’t close
- vertebrae fail to develop properly
- meninge seal forms and balloons out
- neurones grow into it and become damaged
- folic acid has a 90% success rate at preventing this
13
Q
How do the different areas of the brain develop? 5
A
- 3 swellings at rostral end of neural tube, which become three primary vesicles
- prosencephalon/forebrain
- mesencephalon/midbrain
- rhombencephalon/hindbrain
- forebrain grows into two telencephalic vesicles, diencephalon and optic vesicles
14
Q
What are ventricles in the brain? 2
A
- hollow and filled with cerebrospinal fluid
2. fluid formed in choroid plexus
15
Q
Do you know the arrangement of the brain and spinal cord?
A
good effort
16
Q
What is the brainstem? 5
A
- oldest and most primitive part of the brain
- contains decision matrix and controls vital functions
- contains midbrain - relay region
- midbrain is involved in movement, sensory input eg eyes and ears
- also contains hindbrain
17
Q
What is the hindbrain? 3
A
- Pons - switchboard which connects cerebellum to cerebral cortex
- Medulla - autonomic functions
- Cerebellum - not really a true part of the hindbrain, sticks out behind it
18
Q
Describe the pons and medulla. 4
A
- pons swells out from ventral surface of brain stem
- contains many cell bodies
- important relay between cortex and cerebellum
- medulla is important in control of bp and respiration
19
Q
What is the impact of brain stem damage? 4
A
- hydrocephalus (liquid on brain) and haemorrhage increases pressure in the head
- fluid can’t escape from fused skull
- severe cases can lead to coning of stem
- damage to medulla leads to respiratory arrest
20
Q
What is decussation. 4
A
- crossing over of neurons in medullary pyramids
- corticospinal tract crosses over in medulla
- right hemisphere controls left body
- left hemisphere controls right body
21
Q
What is the cerebellum? 5
A
- old/primitive brain part
- movement control centre incl fine movement
- extensive connections to cerebrum and spinal cord - 2x more neurons than both cerebral hemispheres
- diseases incl ataxias - aberrant movement coordination
- one 24year old survived this long without one!
22
Q
what are the diencephalon and the mesencephalon? 5
A
- midbrian has linkagesbetween components of motor systems eg. substantia nigra
- substantia nigra is damages in parkinson’s
- diencephalon contains thalamus and hyopthalamus
- thalamus - relay and gating roles
- hypothalamus - homeostasis and reproduction
23
Q
What is the cerebral cortex? 5
A
- clear division between halves along sagittal fissure
- Controls:
- voluntary actions
- cognition
- perception/awareness - mammals have a more complex, 6 layered (vs 1) neocortex
- allows more nerves so more intelligence
- different sizes but same general structure
24
Q
What is cortical folding? 6
A
- more processing power needed for more intelligence
- cortical neurones represent processing power
- skull is a confined structure so volume and mass should be kept to a minimum
- big heads are more difficult to protect
- sheet of cortex folds into gyrus (peak) and sulcus (trough)
- central sulcus goes laterally-medially
25
Q
Describe the lobes of the cerebral cortex.3
A
- different parts have different functions
- pre-central gyrus - motor and post-central gyrus - sensory
- cortical lobes clockwise from rostral:
- – frontal
- parietal
- occipital
- temporal
26
Q
What is the homunculus? 3
A
- shows location and amount of neocortex dedicated to particular function
- proportional to neuronal composition, not body part mass
- inhumans, shows importance of finger movements and speech control
27
Q
What are Electroencephalograms (EEG)? 6
A
- electrodes placed on skull
- brainwaves measured corresponding to activity
- different patterns associated with different things
- epilepsy - random peaks across all
- bleeding - global calming of waves
- fast and cheap but difficult to interpret and poor resolution
28
Q
What is a CT scan? 3
A
- shows large structures and problems
- uses harmful x-ray radiation
- only shows one plane
29
Q
what is magnetic resonance imaging (mri)? 6
A
- strong magnetic field and radiowaves
- higher resolution
- electromagnetic radiation causes protons to switch between increased and decreased energy frequencies, which releases more EMR
- the more detected, the more fluid there is
- covers whole brain without harm
- useful for soft tissues and very expensive
30
Q
What is a PET scan? 3
A
- injection of radioactive glucose
- differential take up depending on brain activity
- hihglights increased brain activity from positron emissions
31
Q
What is an fMRI? 1
A
- Oxyhaemoglobin has a different magnetic resonance to deoxyhaemoglobin
