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Biol125 - Human Physiology > Week 1 > Flashcards

Week 1 Flashcards

(72 cards)

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1
Q

What are the components of the nervous system ?

A

Central nervous system
-brain
-spinal cord

Peripheral nervous system (PNS)
-cranial and peripheral nerves

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2
Q

What is the cerebrum ?

A

It is the largest part of the brain . It contains the cerebral cortex and sub cortical regions

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3
Q

What is the cerebellum ? / where is it located ?

A

Located in the posterior region of the brain
It is mainly responsible for balance and coordination

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4
Q

What is the brainstem ?

A

It contains the midbrain , pons and the medulla oblongata
It communicates with the PNS to control involuntary processes such as breathing and heart rate

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5
Q

The cerebrum is separated into 2 hemispheres that are connected by a large fibre bundle called the ………..

What is the outer layer of the cerebrum composed of ?

What are the 4 functionally and anatomically distinct lobes of the cerebral cortex ?

A

Corpus callosum

The cerebral cortex

Frontal , parietal , temporal , occipital

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6
Q

What is the role of the frontal lobe ?

A

Higher cognitive functions e.g decision making , and problem solving. It is also responsible for some features of language and voluntary movement

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7
Q

What is the role of the parietal lobe ?

A

Integrates information from the visual pathway , coordinates motor movement and interpretation of sensory information

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8
Q

What is the role of the temporal lobe ?

A

Interpreting speech and hearing , object recognition and emotion

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9
Q

What is the role of the occipital lobe ?

A

Processing primary visual information

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10
Q

What are the brain regions that lie under the cortex called ?
What are some of the important subcortical structures called ?
What are some of the functions ?

A

Sub-cortical regions
Hypothalamus
Amygdala
Hippocampus
Thalamus
Basal ganglia

Memory , emotions , motor movement , processing sensory information

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11
Q

What does the midbrain serve as a connection between ?

What does the midbrain consist of ?

A

The brainstem and subcortical regions

Colliculi - directs eye movement towards objects of interest

Tegmentum - coordination of movement , alertness/ sleep

Cerebral peduncle - control of ocular muscles

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12
Q

The spinal cord is divided into 5 main sections , what are these ?

A

Cervical ( neck )
Thoracic ( chest )
Lumbar ( lower back )
Sacral ( hip)
Coccygeal ( tail(

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13
Q

What are the different sections of the peripheral nervous system ?

A

Somatic -
Voluntary - controls the skeletal muscles and provides sensory information from the body and from the outside world

Autonomic -
Involuntary functions

Enteric - regulates movement of water and solutes between gut and tissues

Sympathetic and parasympathetic -
Modulate and balance involuntary functions ( heartbeat, breathing )

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14
Q

Afferent pathways carry sensory information from the periphery to where ?

A

Up to the brain via ascending nerve tracts

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15
Q

The brain sends signals down to the peripheral nerves along what ?

A

Efferent descending nerve tracts to control motor output

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16
Q

When the knee is hit , sensory afferents in the knee send information to ……….

These afferents synapse onto ……. within the spinal cord

The interneurons send information to the muscles of the legs via ……… efferent fibres that originate in the ventral horn

The efferent fibres communicate with the muscles causing them to contract , resulting in a …………

This reflex occurs …………

A

The dorsal column of the spinal cord
Interneurons

Jerk of the leg

Without input from the brain

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17
Q

What cells are part of the CNS ?
What are the 2 main cell groups ?

Around how many neurons and glial cells does the brain contain ?

A

Neurons

Glial cells can be subdivided into :
Astrocytes
Microglia
Oligodendrocytes

Neurons (nerve cells) and glia (support cells )

10 to the power of 11 neurons
10 to the power of 12 glial cells

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18
Q

Describe dendrites -

A

Short, bristle like highly branched processes
Receive nerve input ( at synapses )
Not myelinated

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19
Q

Describe soma (cell body )

A

Contains the normal cell organelles
Main site of protein synthesis and degradation
Has pronounced rough ER = Nissl substance

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20
Q

Describe the axon

A

-long, thin process
-propagates nerve impulse to another neuron , muscle fibre or gland
-often myelinated
-terminates at axon terminals or synapses

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21
Q

How can we structurally classify neurons ?

A

Bipolar neurons - 1 main dendrite and 1 axon
E.g retina of the eye , inner ear , olfactory area of the brain

Unipolar neurons - just 1 process from the cell body , part way down the axon
E.g sensory neurons ( pain , temperature , touch and pressure )

Multipolar neurons - many dendrites and 1 axon

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22
Q

What are micro-glia ?
What are the two forms ?

A

Immune cells that survey the CNS and respond to signs of infection or damage

They exist in a wide-range of morphologies depending on activation state

Surveillant = smaller with multiple processes

Activated = larger , with rounded cell body and shorter processes

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23
Q

What are astrocytes ?

A

Small, star shaped cells that provide support for the development and homeostatic maintenance of the nervous system and cerebral blood vessels

Heterogeneity - morphology , protein expression across different brain regions

Form a glial scar after severe injury

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24
Q

What are oligodendrocytes ?

A

Cells that form the lipid-rich sheath of myelin that wraps around some neurons to increase the speed at which information is transmitted by the neuron

In the PNS , these cells are called Schwann cells

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25
What does white matter contain ?
Areas of brain that contain myelin ( bundles of axons )
26
What does grey matter contain ?
Unmyelinated cell bodies
27
What are blood vessels in the brain made up of ?
Endothelial cells , astrocytes , pericytes (capillaries ) , smooth muscle cells ( arteries ) and neurons = neurovascular unit
28
What is the physical barrier between the blood and the brain called ?
Blood-brain barrier (BBB) , due to tight junctions
29
Where is cerebrospinal fluid contained ?
Within the ventricles and in the subarachnoid spaces of the brain and spinal cord
30
What is the function of CSF?
It provides buoyancy for the brain and cushion it against injury , as well as waste removal
31
What is CSF produced from ?
Filtered blood by the choroid plexus in the ventricles
32
Why is a CSF sample able to be used to provide a ‘snapshot’ of the brain environment ?
Because CSF is shared between the brain and the spinal cord
33
Which part of a neurone receives information ? In what form are electrochemical signals / nerve impulses transmitted along the axon ?
Dendrites 100,000 synaptic inputs/neurons Action potentials
34
Describe the chemical and the electrical forces which act on an ion and how they combine to form the electrochemical force ?
Chemical - differences in concentration , diffusion from a region of high concentration to a region of low concentration Electrical - interior of the cell is - charged , + cations are retained and negative ions will be expelled
35
What are the two broad categories of ion channels ?
Channels that are gated that require a stimulus to open - ligands , mechanical force or voltage -specific to a particular ion Channels that are always open - they allow free movement of ions
36
Is the flow of K+ constant ?
Yes the flow of K+ is constant from the inside of the neuron to the outside
37
In the Na+/K+ pump , 3Na+ ions are moved from where to where ? 2K+ ions ? Overall effect on the cell ?
Inside of the cell to the outside of the cell 2K+ ions moved from outside the cell to the inside Overall , there is loss of 1Na+ ion to the extracellular environment with every cycle
38
What is the difference in charge across the membrane of the neurone referred to as ?
Polarisation
39
What is the difference in VOLTAGE across the plasma membrane when the neurone is at rest called and what is this voltage ?
Resting membrane potential -70mV
40
What is the equilibrium potential ?
Membrane potential required to exactly counteract the chemical forces acting to move one particular ion across the membrane
41
How does K+ still move out of the cell despite the fact that electrical force counteracts chemical force and wants to pull + ions into the cell ?
Chemical force > electrical force , K+ moves out of the neuron
42
What is the Nernst equation ?
Calculates equilibrium potential ( see PowerPoint )
43
E =2.718
44
Above what threshold potential is an action potential stimulated ? What term refers to the membrane potential decreasing ?
-55mV Hyperpolarisation
45
At rest what gate of a voltage gated Na+ channel is open and which is closed ? How many gates do voltage gated K+ channels have ?
Inactivation gate ( activation gate is closed ) One , which opens to allow the flow of K+ ions and closes to stop the flow of K+ ions
46
What happens when the neuron receives an excitatory signal or stimulus ?
Ligand-gated ion Na+ channels open, small amounts of Na+ will move down their conc gradients into the neuron and the resting potential will start to become more positive
47
Once the membrane potential reaches a critical threshold of -55mV what happens ?
voltage-gated activation gates in the Na+ channel open quickly, allowing Na+ to flood into the neuron As a result of the large influx of positively charged Na+ , the neuron quickly loses its negative charge and undergoes depolarisation
48
How are Na+ channels inactivated following depolarisation ?
Na+ channel is plugged by the inactivation gate
49
Describe repolarisation
Neuron becomes sufficiently positive , voltage-gated K+ channels open slowly , K+ flows down its conc gradient out of the cell Neuron quickly regains its negative charge in a process called re polarisation
50
What causes the membrane potential to become more negative than the resting potential ?
Hyperpolarisation due to an extra efflux of K+ as the voltage gated K channels closing is a slow process
51
What is the refractory period ?
During this period , the neuron will not be able to fire another action potential Na+/K+ ATPase pump will restore the resting potential to -70mV
52
53
In what region of the neuron are action potentials initiated ?
Axon hillock
54
55
What term describes how an action potential can jump between nodes of Ranvier ?
Saltatory conduction
56
What is the difference between chemical and electrical synapses ?
Chemical - release of neurotransmitters from a pre-synaptic neuron that diffuses across the synaptic cleft and binds to post-synaptic neurons Electrical synapses - use gap junctions that directly connect the cytoplasm between 2 cells
57
What is the first stage that occurs after depolarisation of the action potential reaches the presynaptic terminal ? What step follows this ?
The voltage-gated Ca2+ ion channels open Vesicles containing neurotransmitters fuse with the plasma membrane of the neuron. Causing the neurotransmitter to be released into the synapse.
58
What occurs once neurotransmitter has diffused across the synapse and bound to receptors on the postsynaptic neuron ?
For excitatory neurotransmitters , Na+ channels open leading to an action potential in the postsynaptic neuron.
59
What 2 things can occur to terminate synaptic communication ?
Neurotransmitter is either taken back up into the presynaptic neuron (reuptake) or broken down in the synapse by enzymes
60
What do EPSP and IPSP stand for ? What is summation
EPSP = excitatory postsynaptic potential IPSP = inhibitory postsynaptic potential The process by which the neuron ‘sums up’ all the excitatory and inhibitory signals it receives over a period of time
61
What are the criteria for a transmitter substance ?
1. Synthesised in the neuron 2. Present at presynaptic terminals , packaged with synaptic vesicles 3. Exogenous substance ( drug) at reasonable concentration mimics exactly the action of endogenously released transmitter 4. Specific mechanism exists for removing transmitter from synaptic cleft
62
Is acetylcholine excitatory or inhibitory ? Where is the secretion site ?
At skeletal muscle it is excitatory It can be either at other sites CNS and PNS Neuromuscular junction
63
Are the biogenic amines ( norepinephrine,epinephrine , dopamine , serotonin ) excitatory or inhibitory ? Where is their secretion site ?
(Nor)epinephrine - Excitatory or inhibitory CNS and PNS Dopamine - generally excitatory CNS and PNS Serotonin ( 5-hydroxytryptamine, 5-HT) - generally inhibitory CNS
64
65
Are the amino acid neurotransmitters Excitatory or inhibitory ? Secretion sites ?
Gamma aminobutyric acid (GABA) - inhibitory CNS and neuromuscular junction ( of invertebrates ) Glycine - inhibitory - CNS Glutamate - excitatory - CNS _ neuromuscular junction of invertebrates Aspartate - excitatory - CNS
66
Are the peptide neurotransmitters excitatory or inhibitory ?
Substance p = excitatory CNS and PNS Met-enkephalin = generally inhibitory - CNS
67
What are the 2 main type of neurotransmitter receptors ?
Ionotropic - transmitter binding - direct opening of ion channel Always stimulatory Fast - effect lasts a few milliseconds Metabotropic receptors - transmitter binding - indirect activation of G-protein -G-protein coupled receptors - can trigger opening or closing of a separate ion channel and downstream signalling cascade -slow - effect takes up to several hours
68
Describe the structure of ionotropic receptors Give some examples
Composed of 4 or 5 subunits arranged around a central pore in the membrane Receptors can be made up of different combinations of subunits = increased diversity between different tissues Nicotinic acetylcholine GABA Glycine
69
Describe the structure of a metabotropic receptor
Composed of a single protein with 7 membrane spanning regions ( alpha helices ) E.g muscarinic acetylcholine Alpha and beta adrenergic receptor All 5-HT receptors except 5-HT3 Rhodopsin Olfactory receptors Many others
70
Describe the summary of sequence of events of G protein activation
1. Transmitter binds to receptor 2. GTP exchanged for GDP on the G protein alpha subunit 3. G protein dissociates from the receptor - then the ligand as well 4. The 3 subunits (alpha, beta and gamma) of the G protein also dissociate 5. The alpha subunit activates the ion channel 6. The alpha subunit is inactivated by the hydrolysis of GTP to form GDP (GTPase activity is intrinsic to this subunit ) 7. The alpha subunit recombines with Beta and Gamma subunits and attaches to the receptor , which can then bind another agonist
71
What are agonists ? Antagonists ?
Agonists = drugs that mimic the action of the neurotransmitter Antagonists = drugs that block the action of the neurotransmitter
72

Biol125 - Human Physiology (4 decks)

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