How do we control ourselves? Flashcards by Hannah Logan

What are the functions of the Nervous System?

Maintaining homeostasis
Receives sensory input
o Internal
o External
Integrating information
Motor output
Establish and maintain mental activity

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What are the structural divisions of the nervous system?

-Central nervous system (CNS)
o Brain and spinal cord
-Peripheral nervous system (PNS)
o Spinal nerves and cranial nerves

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What is a Neuron, Axon, Nerve & Sensory Receptors?

Neuron (nerve cell): basic structural unit of the nervous system
Axon: nerve fibre
Nerve: bundle of axons (or nerve fibres) and their sheaths (outer covering)
Sensory receptors: separate specialised cells which detect temperature, pain, touch, pressure, light, sound, odour and other stimuli

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What is a Action Potential, Effector organ/cell, Ganglion, Plexus and Synapse?

Action potential: electrical signal
Effector organ or effector cell: the organ, tissue or cell in which an effect or an action takes place
Ganglion: collection of cell bodies located outside the CNS
Plexus: extensive network of axons or cell bodies
Synapse: junction of a neuron with another cell e.g. end of a neuron with a muscle cell or another neuron

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Describe the Autonomic nervous system.

Involuntary and under subconscious control
Action potentials in the motor neurons travel from the CNS to smooth or cardiac muscle, or glands
Two-neuron system
Cell bodies of the neurons are located in the CNS and autonomic ganglion

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Describe the Somatic nervous system

Voluntary and under conscious control
Action potentials in the motor neurons travel from the CNS to skeletal muscles
Single neuron system
Cell bodies are located in the CNS

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What are the cells of the NS (CNS & PNS)

-Neuron
-Neuroglia
CNS
-Astrocytes
-Ependymal cells
-Microglia
-Oligodendrocytes
PNS
-Schwann cells
-Satellite cells

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Describe the structure of a Neuron

-Structural unit of the nervous system
-Dendrites
o Dendritic spines
-Cell body (soma)
-Axon
o Axon hillock
o Initial segment
o Trigger zone
o Axon collaterals
o Axon terminal or presynaptic terminal
o Terminal boutons or synaptic knobs

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What are the types of neurons in terms of function?

Sensory (afferent) neuron – information to the CNS
Motor (efferent) neuron – information away from the CNS
Inter-neuron – information from one neuron to another neuron

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What are the types of neurons in terms of structure?

Multipolar
Bipolar
Unipolar

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What are Astroycyte Cells?

Forming a supporting framework for blood vessels and neurons
Assists in the formation of tight junctions between endothelial cells of the capillaries
Respond to tissue damage in the CNS

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What are Ependymal Cells?

-Line the central cavities of the brain and spinal cord

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What are Microglial Cells?

Monitor the health of surrounding neurons

- Phagocytose microorganisms, infection, trauma or inflammation

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What are Oligodendrocytes?

-Cover axons which forms an insulating sheath around them → myelin sheath

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What are Schwann Cells?

Also called neurolemmocytes
Form a myelin sheath around axons
Insulating

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What are Satellite Cells?

Provide support and nutrition to cell bodies in ganglia

- Protect cell bodies from harmful substances

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What is in the Grey Matter in the CNS & PNS?

CNS: Brain= Outer cortex of brain & nuclei
Spinal Cord= Inner ‘grey’ part
PNS:Ganglion

What is in the White Matter in the CNS & PNS?

CNS: Brain=Deeper nerve tracts
Spinal Cord=Outer part
PNS:Nerves

What is a membrane potential?

-Membrane potential= the difference in charge across the cell membrane

What characteristics of a cell membrane allow a membrane potential to occur?

Differences in ionic concentration (particularly for Na+ and K+ ) across the cell membrane
Permeability of the cell membrane to ions

What are non-gated ion channels?

Also known as ‘leak’ ion channels
Ion specific
Cell membrane has more K+ leak ion channels compared to Na+ leak ion channels

What are gated ion channels?

Gated ion channels – require signals to open them
Ligand-gated ion channel
Voltage-gated ion channel
Other-gated ion channel

What is a resting membrane potential?

-Resting membrane potential – the difference in charge across the cell membrane in a resting cell

What occurs at a resting membrane potential?

Intracellular side is more negative
RMP of neurons = - 70 mV where the negative sign indicates the charge on the intracellular side of the cell.
RMP caused by leak ion channels and the Na+/K+ pump

What is Depolarisation, Hyperpolarisation and Repolarisation?

Depolarisation – when the membrane potential becomes more positive i.e. the inside of the cell becomes more positive. E.g. - 70 mV  - 30 mV Hyperpolarisation – when the membrane potential becomes more negative i.e. the inside of the cell becomes more negative. E.g. - 70 mV  - 75 mV Repolarisation – membrane potential returns to normal

What is a graded potential?

- Graded potentials can lead to action potentials - Graded potential – short-lived, localised changes in membrane potential - Often occur in dendrites or the cell body of a neuron - Ability to summate - Decremental - Not able to transfer information over long distances

What is afterpotential?

Afterpotential – short period of hyperpolarisation of an action potential

What is the first step of the operation of the gates?

1. Resting membrane potential: - All gated Na+ and K+ channels are closed. - K + leak channels (not visible on this image) are open which allow movement of K+ to the outside of the cell. This creates a negative intracellular charge = RMP. - Na+ /K+ pump (not visible on this image) also creates the RMP.

What is depolarisation in the operation of the gates?

2. Depolarisation: - Na+ gated channels open and Na+ moves into the cell and inside of the cell becomes more positive. - K + gated channels are closed. - Membrane potential becomes more positive.

What is repolarisation in the operation of the gates?

3. Repolarisation: - Na+ gated channels close. - K + gated channels open and K+ moves out of the cell and the intracellular side becomes more negative. - Membrane potential becomes more negative.

What happens at the end of repolarisation and the afterpotential in the operation of the gates?

4. End of repolarisation, and the afterpotential: - Na+ gated channels close. - K + gated channels close as well but they close slowly so K+ continues to leave the cell and this produces the afterpotential. - Membrane potential becomes very negative.

What happens at the resting membrane if the operation of the gates?

5. Resting membrane potential: - Na+ gated channels are closed. - K + gated channels are closed. - Resting membrane potential is re-established by Na+/K+ pump (an active process as it is against their concentration gradients) which redistribute ions as all Na+ and K+ gated channels are closed.

What dose the refractory period consist of?

- Absolute refractory period | - Relative refractory period

Where does the propagation of axon potentials occur and what does it follow?

- This takes place in unmyelinated axons only - Following depolarisation, each segment of the axon membrane becomes repolarised - The propagation of the action potential occurs in one direction

What is Saltatory Conductiomn?

Propagation of action potentials in myelinated axons

What are the parts of a synapse and what are electrical & chemical synapses?

- Junction of a neuron with another cell e.g. end of a neuron with a muscle cell or another neuron - Pre-synaptic - Synapse - Post-synaptic - Electrical synapses → current - Chemical synapses→ chemicals e.g. hormones, neurotransmitters

How are neurotransmitters removed?

- Breakdown by enzymes - Re-absorption back into the presynaptic terminal - Diffuse away from the synapse

What are reflexes?

- Automatic response to a stimulus - Are somatic or autonomic - Are homeostatic

What are the components of reflexes?

- Sensory receptor - Sensory neuron - Interneuron - Motor neuron - Effector organ

What are the types of reflexes?

- Stretch (monosynaptic) - Golgi tendon - Withdrawal