Richard (Neurophysiology) Flashcards
What are the definitions of the following?:
- Nerve impulse
- Motor unit
- Axon
- Axon terminal
- Neuromuscular junction
- Synaptic cleft
- Acetylcholine (ACh)
Nerve impulse- 1 nerve cell stimulates many muscle cells
Motor unit- 1 neutron and muscle stimulated cells
Axon- extension of neuron
Axon terminal- end of Xon
Neuromuscular junction- where axon terminal meets muscle fibre
Synaptic cleft- space between neutron and muscle fibre
Acetylcholine- neurotransmitter
What does the nervous system split into?
Peripheral nervous system (PNS) (involves cranial nerves and spinal nerves, communication lines between the CNS and the rest of the body) and Central nervous system (CNS) (involves brain and spinal cord, integrative and control centres)
What does the PNS split into?
Sensory (afferent) division (somatic and visceral sensory nerve fibres, conducts impulses from receptors to the CNS) and motor (efferent) division (motor nerve fibres, conducts impulses from the CNS to effectors)
What does the motor division split into?
Autonomic nervous system (involuntary, conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands) and somatic nervous system (voluntary, conducts impulses from the CNS to skeletal muscles)
What does the autonomic split into?
Sympathetic division (arousing, mobilises body systems during activity) and parasympathetic division (calming, conserves energy, promotes house-keeping functions during rest)
Neuroglia
Neuroglia are a large class of neural cells including astrocytes, microglia, oligodendrocytes, and ependymal cells.
- Astrocytes- most abundant, versatile, and highly branched glial cells. Cling to neutrons, synaptic endings, and capillaries.
- Microglia- small, ovoid cells with thorny processes that touch and monitor neurones. Migrate towards injured neurones. Can transform to phagocytise microorganisms and neuronal debris. (Same function as macrophages but work in the brain)
- Oligodendrocytes- branched cells. Form myelin sheath in CNS. (In PNS Schwann cells form myelin sheath)
- Ependymal cells- range in shape from squamous to columnar. May be ciliated. Line the central cavities of the brain and spinal column. Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells.
What is the difference between neurone and neuroglia?
Neurones are like the communication network of the body whereas neuroglia facilitate the functioning of the communication network.
Neurons
Nerve cell. Structural units of nervous system. Large, highly specialised cells that conduct impulses. Extreme longevity. Amitotic (division of cells without mitosis). High metabolic rate so requires continuous supply of oxygen and glucose. All have cell body and one or more processes.
Contains a cell body (soma), dendrites (receive information), axon (only 1 per neurone, transmit stimulus), axon terminal.
How is an electrical impulse passed along a somatic motor neurone and an autonomic motor neurone?
Somatic- Spinal cord -> through myelinated motor neurons -> ACh -> effector
(ACh: contraction of skeletal muscle)
Autonomic- Spinal cord -> through myelinated preganglionic neurone -> to autonomic ganglion ->through unmyelinated postganglionic neurone -> ACh -> effector
(ACh: contraction of smooth or cardiac muscle, stimulation or inhibition of glandular secretion)
Membrane potential
The charge is negative inside the cell and positive outside the cell. There are more NA+ ions outside and K+ inside.
Resting membrane potential
Requires
1- intact cell (semi-permeable) membrane
2- ionic concentration gradients and ionic permeability’s (particularly K+ ions)
3- over the long term: metabolic processes
Ionic concentration gradients
Intracellular
- 12M Na+
- 125mM K+
- 5mM Cl-
- 108mM anions
Extracellular
- 120mM Na+
- 5mM K+
- 125mM Cl-
Ek (resting potential for ideal membrane)
(don’t really need to know- not clear on the ppt)
Nernst equation is used to calculate Ek.
The membrane potential at room temperature is calculates to be -58mV.
Reducing K+ concentration gradient reduces the electrical gradient to balance. Ideally the membrane is impermeable to Na+ ions and therefore changing concentration will not effect Em.
Em is usually less negative than Ek.
This is because the cell membrane is not completely impermeable to Na+ so Na+ moves in and there is K+ leakage so K+ moves out. These movements depolarise the membrane potential.
Na+/K+ pump
For every 2 K+ ions that are pumped into the cell 3 Na+ ions are pumped out. This requires ATP. ATP -> ADP + Pi
Transport across membranes
Diffusion
Facilitated diffusion
- ligand gated e.g. Cl- Ca2+
- mechanically gated e.g. Ca2+ Na+
- voltage gated e.g. Na+ K+
Active transport
