How do we control ourselves? Flashcards
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
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
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
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
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
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
What are the cells of the NS (CNS & PNS)
-Neuron
-Neuroglia
CNS
-Astrocytes
-Ependymal cells
-Microglia
-Oligodendrocytes
PNS
-Schwann cells
-Satellite cells
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
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
What are the types of neurons in terms of structure?
- Multipolar
- Bipolar
- Unipolar
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
What are Ependymal Cells?
-Line the central cavities of the brain and spinal cord
What are Microglial Cells?
- Monitor the health of surrounding neurons
- Phagocytose microorganisms, infection, trauma or inflammation
What are Oligodendrocytes?
-Cover axons which forms an insulating sheath around them → myelin sheath
What are Schwann Cells?
- Also called neurolemmocytes
- Form a myelin sheath around axons
- Insulating
What are Satellite Cells?
- Provide support and nutrition to cell bodies in ganglia
- Protect cell bodies from harmful substances
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?
- 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?
- 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?
- 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?
- 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?
- 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
