Fundamentals of the nervous system Flashcards
What do the sensory and motor systems detect/ control?
Sensory= sensations of pain, temperature, touch and special senses such as vision and hearing
Motor= reflexes and voluntary movement as well as tone posture and coordinated movement
What are the two main pathways of the sensory systems?
The dorsal column pathway
The spinophalamic pathway
What information does the dorsal pathway carry, and where does it travel?
Carries proprioception (sense of movement, action and location)
Also carries vibration and fine touch
Travels dorsally to the spinal cord, then onto the thalamus and the primary somatosensory cortex
What information does the spinothalamic pathway carry and where does it travel?
Carries info about pain, non-discriminative touch and temperature
Is anterlaterol to the spinal cord then reaches thalamus and primary somatosensory cortex
What is the topographic organisation in the primary somatosensory cortex/ homunculus?
Diagram that represents where and what proportion of the somatosensory cortex a certain body part is
Medial of brain- lower limb
Lateral brain- hands and face
What collects data for a cell body and and what do cell bodies have lots of?
Dendrites gather information from other neurones then a single axon transfers this data.
They require huge amounts of energy thus have large amounts of mitochondria
What are the gaps in myelination of nerves called?
Nodes of ranvier
What is the process of carrying neurotransmitters from cell bodies towards the synapse called?
Anterograde axonal transport
What are the steps for a neurotransmitter to be released over the synaptic cleft?
When a AP reaches the axon terminal, this triggers voltage gated calcium channels which open and Na floods into the cell.
This triggers exocytosis- fusion of synaptic vesicles with the membrane of the synaptic cleft
Neurotransmitter is released and diffuses across the synaptic cleft
Binds to receptors in post synaptic cells, and induces a electrical/chemical response
What are the pores through which electrical impulses can travel in tight junctions?
Connexons
What are the cells that provide myelination in the PNS?
Schwann cells
Type of glial cell, provide support and protection to the neurons, maintains homeostasis, cleans up debris, and forms myelin
1:1 ratio to axon cells
What is myelin?
Layers and layers of lipid and protein wrapped around the axon
Allows electrical impulses to transmit quickly and efficiently along the nerve cells
What is the CNS myelinating cell?
Oligodendrocyte
Glial cell; provides support and protection to the neurons, maintains homeostasis, cleans up debris, and forms myelin
Associates with < 1 axon at a time
What is the function of astrocytes?
Equivalent of fibroblasts
Central to blood brain barrier integrity, protect nervous system from the blood
What are the microglia?
Resident macrophage of the CNS
Has a complex role in development, immune surveillance, disease response and tissue repair
What side of the cell is positive and what is negative at resting membrane potential?
Negative on the inside, positive on the outside
What is roughly the resting membrane potential?
-70 millivolts
What are the different sections of an action potential?
After stimulus depolarises mebrane, volatge gated Na channels open- DEPOLARISATION. Overshoots and becomes > 0
Then voltage gated Na channels close and K channels open- REPOLARISATION. K ions flood out of the cell
This overshoots and causes hyperpolarisation, REFRACTORY PERIOD, where no new AP can be induced until back to resting membrane potential
What are the two ways in which an action potential can be triggered?
(1) Locialised ion channels change state due to ligands (ligand gated channels0 or voltage (voltage gated channels)
(2) propogation of charge from a adjacent region
What information is carried in unmyelinated fibres?
Dull pain and temperature sensation- in C fibres
What is an inhibitory neurotransmitter and what is an example?
Inhibitory neurotransmitters block or prevent the chemical message from being passed along any farther.
GABA- linked to Cl channels so hyperpolarises the cell making it difficult for an AP to fire. Alcohol and benzodiazepines are GABA like molecules
What are examples of excitory neurotransmitters?
Glutamate, acetylcholine, noradrenaline, serotonin and dopamine
What receptors does acetylcholine act apon?
Nicotinic (fast acting) and muscarinic (slow acting)
What occurs at a neuromusular junction?
ACh is released into the synaptic cleft and is rapidly degraded by acetylcholinesterase
AChR binding causes ion channels to open up at the end motor plate of the muscle fibre
Results in a Na influx and a K efflux which causes depolariation of muscle- an AP is formed
What is the repeating unit of a muscle called and what is it comprised of?
SARCOMERE
Comprised of a z disk, thin (actin) and thick (myosin) filaments
How is actin blocked from interacting with myosin in a muscle?
Tropomyosin, which in turn is controlled by troponin
How does an action potential cause muscle fibres to contract?
AP extends down T-tubules, and once it reaches the sarcoplasmic reticulum, it triggers a release of Ca ion release
Ca binds to troponin which unblocks the action of tropomyosin, allowing actin and myosin to interact
Myosin heads alternatively attach and detach, pulling thr actin fibres towards the centre of the sarcomere
How is muscle contraction stopped?
Ca is actively removed by uptake in the sarcoplasmic reticulum, causing tropomyosin to block actin again
What are the 3 stages of the build of muscle contraction?
What are the different types of muscle fibres?
Slow twitch
Fast fatiguable
Fast and fatigue resistant
People with slow twitch muscle fibres better at low intensity, longer activities
What is the test done to measure muscle function?
Insert micro-electrodes into the muscle= ELECTROMYOGRAPHY
What part of the embryo is the nervous system dervived from?
The ectoderm
What is neuralisation?
The notochord sits in the middle of the embryo. Sends out chemical signals that stimulate the ectoderm to rise up at the edges and form a neural groove.
Then curls up to form the neural tube.
What are some different neural tube defects?
Anencephaly- failure of fusion at the head. Not compatible with life
Spina bifida- failure of fusion at the bottom of the spinal cord
What is a risk factor for neural tube fusion failure?
Foliate deficiency
What are the 3 primary brain vesicles in development?
Forebrain- prosencephalon
Midbrain- mesencephalon
Hindbrain- rhombencephalon
What happens to the 3 primary brain vesicles in week 5 of development?
What is neurogensis and gliogegenesis?
The making of new neurones and glial cells
Where are neurones made in the brain?
Made deep in the brain- they then migrate towards the cortical surface of the brain where they will stay and form grey matter
What does failure of neuronal migration lead to?
Pockets of grey matter stay deep within the brain
Known as heterotopia
Can lead to epilepsy
When does neurogenesis and gliogenesis occur during development?
Weeks 4-12
When does neuralation occur in development?
Weeks 3-4
When does neural migration occur during development?
Weeks 12 until birth
