Nervous System Flashcards
What are the two systems in the nervous system?
Central nervous system
Peripheral nervous system
What is involved in the central nervous system?
Brain and spinal cord
What is involved in the peripheral nervous system?
Afferent nerves
Efferent nerves
What are the two types of efferent nerves?
Somatic
Autonomic
What are the building blocks of the nervous system?
Neurones
Oligodrendrocytes/ Schwann cells
Astrocytes
Microglia
What is a neurone?
Responsible for communication
Have a lipid sheath called myelin
What are oligodrendrocytes/ Schwann cells?
Facilitate transmission
Produce myelin
What are astrocytes?
Enable homeostasis
Reuptake of neurotransmitters
Support neurones
What are microglia?
Immune cells of the brain
Phagocytise dead cells and debris
What do afferent neurones do?
Signals from the periphery to CNS
What do efferent neurones do?
Motor neurones: signals from CNS to the muscle/skin
Autonomic neurones: signals from CNS to smooth muscle/ glands
What do interneurons do?
Connect brain and spinal cord
What triggers release of a chemical signal (neurotransmitter) at the end of a synapse?
Electrical action potential
What do neurotransmitters do after being released?
Bond to post synaptic receptors, triggering depolarisation of the post synaptic neurone.
What are the two main types of neurotransmitters?
Excitatory neurotransmitters
Inhibitory neurotransmitters
What physical things protects the brain?
Cranium
Meninges
What is cerebrospinal fluid (CSF)?
Salty solution secreted into ventricles by choroid plexus
Physical protection by its buoyancy and padding
Chemical protection by being a stable ionic environment
How is the blood supplied to the brain?
Nervous tissue
Requires O2 and glucose
15% of blood supply to the brain
How does the blood brain barrier(BBB) protect the brain?
Capillaries less permeable
Protects from fluctuations in the blood
Capillary walls have tight junctions
Made from endothelial cells that reproduce themselves constantly
What is the grey and white matter in the brain and spinal cord?
Grey matter= neurone cell bodies
White matter=bundles of axons
What are the 4 regions of the spinal cord?
Cervical
Thoracic
Lumbar
Sacral
What is the distinct pattern in the spinal cord?
Sensory neurones enters via dorsal
Motor neurones leave via ventral
What are the 2 peripheral nerves from the spinal cord?
Spinal nerves
Cranial nerves
What are the 4 parts of the human brain?
Brain stem
Cerebellum
Diencephalic
Cerebrum
What is the function of the brain stem?
Involuntary functions
Blood pressure
Breathing
Vomiting
Sleep
What is the use of cerebellum?
Co-ordinates movement
What is the use of the diencephalon?
Rules homeostasis between the brain stem and cerebrum
What is the use of the cerebrum?
Higher functions
What does the autonomic nervous system do?
Maintain internal environment
Mainly involuntary
Contains visceral functions
What is ANS input?
Sensory neurones from peripheral organs to centres in hypothalamus, medulla
What is ANS input?
Sympathetic or parasympathetic neurones
Generally opposing actions
What do visceral sensory neurones do?
Monitor temperature, pain, irritation, chemical changes and stretch in the visceral organs
Run together with autonomic nerves
What do ANS control?
Mainly smooth muscle, cardiac muscle and secretory glands
How do visceral sensory neurones communicate?
Visceral reflex arcs
Most spinal reflexes such as deflection and micturition reflexes
What are the divisions of ANS?
Sympathetic
Parasympathetic
What type of reaction does sympathetic neurones give?
Fight or flight
Short term survival
Increases in energy availability
What type of reaction does parasympathetic neurones give?
Set and digest
Long term survival
Reduces energy availability
What are the parts involved in the ANS neurone?
Preganglionic neuron
Postganglionic neuron
What qualities does the preganglionic ANS neurone have?
Myelinated
Cholinergic(PNS)
What qualities does the postganglionic ANS neurone have?
Nonmyelinated
Cholinergenic ( PNS)
Adrenergenic (SNS)
What are the differences in location of the PNS and the SNS?
PNS: brain stem, sacral
SNS: thoracic, lumbar
What does PNS neurone release?
Acetylcholine
What does SNS neurone release?
Noradrenaline
What are receptors?
Protein structures that receive and transducer signals
What are ionotropic receptors?
Include ligand gated ion-channel
What are metabotropic receptors?
G-protein linked receptors
What are the 3 acetylcholine receptors?
Nicotinic
Muscarinic
Adrenoceptors
What does the somatic nervous system do?
Controls voluntary muscles
Part of peripheral nervous system
Controls centres in the brain
What are ascending tracts?
Relay information from the spinal cord to the sensory cortex
What are descending tracts?
Relay information from the motor cortex to the spinal cord.
What are neuromuscular junctions?
Synapse of a somatic motor neurone and a muscle fibre
What is the neurotransmitter at skeletal muscle neuromuscular junctions (NMJ)
Acetylcholine (release of the synaptic vesicles)
What does acetylcholine bind to at the neuromuscular junctions?
Nicotinic acetylcholine receptor
What is the post synaptic membrane termed as?
Motor End Plate (MEP)
What cells surround the synapse?
Schwann
What is the somatic type of muscle?
Skeletal
What are the two types of autonomic muscle?
Cardiac
Smooth
What are the main structures of a muscle fibre?
Myofibril
Plasma membrane
Transverse tubule
Terminal of cisternal of sarcoplasmic reticulum
Tubules of sarcoplasmic reticulum
Cytoplasm of a muscle fibre called sacroplasm
What are the four main proteins involved in contraction?
Myosin
Actin
Trocponin
Tropomyosin
What does actin do?
Makes up the thin filament
What does troponin do?
Binds Ca2+
What does tropomyosin do?
Stimulates muscle to contract
In an ultrasound of muscle what does 1 sacromere indicate?
What actually contracts
In an ultrasound of the muscle what does the gap between filaments indicate?
Rest (H zone)
What does an A bond indicate in an ultrasound of the muscle?
Length of the myosin fibrils
What is the sliding filament theory?
H zone gets smaller
Z-line overlapping
This indicates contraction
What are the steps in cross-bridge cycling?
- ATP binds to myosin
- Myosin hydrolyses ATP
- Power stroke
- Myosin releases ADP
What happens when ATP binds to myosin in the cross bridge cycling?
Actin is released as there are two binding sites on myosin
What happens when myosin hydrolyses ATP in the cross-bridge cycling?
Energy from ATP rotates the myosin head to the cocked position
Myosin binds weakly to actin.
What happens in the power stroke in the cross-bridge cycling?
Ca2+ binds to troponin
Begins when tropomyosin moves off the binding sites
What happens when myosin releases ADP in the cross-bridge cycling?
Energy from hydrolysing ATP moves the tropomyosin over
What are the events in the NMJ when excitation contraction coupling occur?
Resting state
AP arrival
Depolarisation of MEP
Contraction
What are the events during a muscle twitch after a single nerve activation?
Latent period?
Contraction
Relaxation
What happens in the latent period during a muscle twitch after a single nerve activation?
Depolarisation transmitted down T tubules
Ca2+ channels open in sarcoplasmic reticulum
Increase in ca2+ in the sarcoplasmic reticulum
Ca2+ binds to troponin revealing myosin binding site on actin
What happens in the contraction period of a muscle twitch after single nerve attraction?
Myosin binds to actin, moves and reforms many times causing sarcomeres to shorten.
What happens in the relaxation period of a muscle twitch after a single nerve attraction?
Ca2+ actively transported back into sarcoplasmic reticulum
Troponin-tropomyosin complex blocks myosin binding
Muscle fibres lengthen passively
What are the three basic principles of muscular contraction?
All or nothing
Threshold
Recruitment
What does recruitment of force depend on?
The number of active muscle fibres
What does the lowest frequency of stimulation do to the muscle fibres?
Muscle fibres relax fully before next AP arrives
What do high frequency of stimulation do to muscle fibres?
No time for the muscle fibres to relax before next AP arrives
What does skeletal muscle contraction red ATP for?
Contraction (cross-bridge forming and release)
Relaxation (pump Ca2+)
Restore Na+ and K+ level after AP
What sources of ATP doe skeletal muscle have?
Phosphocreatine
Carbohydrates
What does a weak stimulus do?
Activates only neurones with low threshold activation
What does a strong stimulus do?
Activates neurones with a higher threshold
What are the two types of muscle fibre twitches?
Slow-twitch
Fast-twitch
What are the properties of a slow-twitch muscle fibre?
Slow contraction
Aerobic metabolism
Fatigue-resistant
What are the properties of fast-twitch muscle fibres?
Rapid contraction
Anaerobic metabolism
Activated in any short lived activity
What causes a muscle cramp?
Hyper excitability of somatic motor neurones- motor unit goes into a state of painful sustained contraction
What are the similarities of smooth muscle and skeletal muscle?
Force-action myosin cross bridge
Contraction
What are the differences between smooth muscle compared to skeletal muscle?
Run in several directions
Slower
Less energy to generate amount of force
Controlled by the autonomic nervous system
No troponin in actin filaments
What are the sections of the cerebrum?
Frontal (reasoning)
Parietal (movement)
Occipital (visual)
Temporal (auditory perception)
what are the cortexes in the control centre in the brain?
The somatosensory cortex and the motor cortex.
the somatosensory cortex interprets the information that is coming in and sends it to the motor cortex for a reaction.
why is the resting membrane potential (-70mV) not the same as what the potential value of k+ ions?
many other ions contribute to the RMP
what are the main differences between volatge activated and ligand activated ion channels?
voltage activated= activated by a change in the voltage, Na and K activated by less negative/ more positive membrane potentials
ligand activated= need the presence of a ligand (ie a neurotransmitter) to open the channel, the channel closes when it diffuses away
what is the difference between the absolute and relative refractory periods?
absolute – when Na channels are closed/in their inactive state
Relative – when the membrane potential is more negative and it is harder to reach threshold
