Week 1 - Overview of nervous system Flashcards
1
Q
Feedback - negative
A
- blood pressure drops
- brain detects change, signals heart to inc HR + constrict blood vessels
- pressure restored
2
Q
Feedback - positive
A
- blood pressure drops
- blood flow to heart dec
- heart unable to pump enough blood to maintain pressure
- blood flow to cardiac muscles decrease
- pressure decreases further
3
Q
neurons
A
- have axons
- receives, generates & transmits electrical signals (impulses)
- Function: cellular communication eg. thinking, controlling, muscle activity
4
Q
grey matter
A
40%
contains:
- neuronal cell bodies
- dendrites
- gigal cells
5
Q
White matter
A
60%
contain MYELIN that surround nerve axons
6
Q
gila
A
- no axons
- Function: homeostasis & neuronal supp.
- outnumber neurons by 25:1
7
Q
neuron - structure
A
- cell body: contain nucleus
- dendrites: receive info
- axons: conduct ELECTRICAL IMPULSES, away from cell body, often wrapped in a MYELIN SHEATH
- axon terminals: release neurotransmitters (chemical signals)
8
Q
neuron - classification
A
sensory (input;PNS) motor (output; CNS)
- interneurons: MODIFY COMMUNICATION → excitatory, inhibitory, local circuit
- PROJECTION NEURONS: connect diff regions of CNS
- distal axon terminals are often specialised
- communication signal propogates from distal to proximal
9
Q
astrocytes
A
- provide STRUCTURAL & NUTRIENT SUPPORT to neuron
- homeostasis role: regulate pH
- connects blood vessels to neurons to form BLOOD BRAIN BARRIER → REGULATE movement from blood to brain (toxins/drugs)
- PREVENTS CNS REGENERATION - from scar tissue when CNs is damaged
10
Q
neurogila
A
Functions: homeostasis, structural support, protein for neurons
$ cell types in CNS, 2 in PNS
11
Q
oligodendrocytes
A
- found in WHITE MATTER
- SUPPORT & ELECTRICALLY INSULATE CNS axons →forming myelin sheaths
- damage produces de-myelination → alters axonal transmission
12
Q
microgila
A
- 1st response of immune system
- become movile & phagocytic: eat cellular debris: rapidly multiplying & changing shape
- found in grey and white matter
13
Q
Schwann cells
A
- found in PNS
- enshcath single PNS axon
- each cell produces part of axon myelin sheath
- gaps between adjacent cells: NODES OF RANVIER
14
Q
satellite cells
A
- Surround neuronal cell bodies in peripheral sensory & autonomic ganglia
- flattened cells
- provide STRUCTURAL & NUTRIENT SUPPORT to neuron
15
Q
ependymal cells
A
- line brain fluid cavities ( ventricles) & central canal in spinal cord
- PRODUCE & CIRCULATE CSF
16
Q
Action potentials - cell membrane
A
- made of phospholipids and proteins → barrier due to HYDROPHOBICITY
- proteins allow cells to communicate → provide pathway across lipid boundary as transporters or ION CHANNELS
- chemical/electrical signals received must CROSS MEMBRANE to generate an electrical potential
17
Q
neuron - communication
A
- STIMULUS on dentrites
- PRODUCTION of potential in cell body
- ACTION POTENTIAL PROPAGATION
- SYNAPTIC ACTIVITY (chemical transmitter) released to synaptic cleft
18
Q
ion channels
A
- ‘leak pores’ : always open, contributes to RMP
Gated channels: closed at rest
- ligand gated: open in response to chemical stimuli acting on receptors on channel
- voltage gated: open to changes in RMP
- stimulus transducing: open to phys. stimulus
19
Q
action potentials - stage 1
A
- resting membrane potential (RMP)
- ions cannot diffuse through plasma membrane; rely on protein channels
exterior: high extracellular Na+, Cl-, low K+
interior: high intracellular K+, low Cl-, Na+
RMP ~ 70mV
20
Q
refractory period - absolute
A
- ONLY when Na+ gates open
- no new stimulus can trigger AP
- sets upper limit on firing frequency
21
Q
ion pumps
A
- contributes to maintenance of RMP
- requires energy to transport ions against conc. gradient
- without it, eventually Na+ influx through leak channels will destroy RMP
- no neurotransmissions
22
Q
action potentials - stage 2
A
- hyperpolarisation (inhibitory)
- RMP becomes more -ve
- no AP possible - depolarisation (excitatory)
- RMP becomes more +ve
- Ap possible is depolarisation is large enough
23
Q
AP propagation - myelinated axons
A
- more energy sufficient - reliable
- SALATORY CONDUCTION: insilating prop. of myelin sheath inc. efficiency & speed
- AP propagates from 1 node of ranvier to next by generating currents that open ion channels
24
Q
AP propagation - unmyelinated axons
A
- passive, slow & unreliable
- ionic current flows across each adgacent segment of membrane
- step by step depolarisation & repolarisation of each voltage gated ion channel in membrane
25
refractory period - relative
- ONLY when K+ gates open
- only supramaximal stimuli will trigger a new AP
- prevent back propagation
26
electical signalling - gap junctions
- less common: bidirectional & fast
- found between adjacent gigal cells, smooth muscle myocytes, gila & some CNS neurons
- alows for synchronising of interconnected neyrons
- can allow small chemical through
27
chemical signalling
- unidirectional pre-to-post synapse
- to complete the signal transfer, a chemical neurotransmitter is released @ synapse to signal next neuron
- post synaptic receptors receive chem. messages ex/in
- slower
28
synapse
- junction between 2 communicating neurons
| - synaptic transmission is a core process
29
summation
TEMPORAL: graded potentials generated by one synapse firing in rapid succession
SPATIAL: graded potentials generated by synaptic transmission of TWO- OR MORE SYNAPSES acting on same neurons
30
neurotransmitters
Glutamate (+)
Gaba/ Glycine (-)
Acetylcholine (+)
31
physiology
- study of functions in living organisms : cellular, systems/organs, pathophysiology
- exercise physiology: study of acute responses + chronic adaptations to a range of physical conditions
- comparative physiology: study across species
