The Autonomic Nervous System Flashcards
What is the role of the nervous system?
-Sense a change, interpret results and respond by co ordinating activities of the body
What is the function of the neurone?
-Communication, action potential, form networks, communicate across a synapse
What is the significance of ion gradients?
-Allow electrical signally and excitability due to the cell membrane being impermeable to ions
Is Ca2+ higher inside or outside of the cell?
-Outside
Is Na+ higher insider or outside the cell?
-Outside
Is K+ higher inside or outside of the cell?
-inside
What is the resting membrane potential?
= -70mV
What are the building blocks of the nervous system?
-Neurone, oligodrenrocytes (CNS), schanncells (PNS), astrocytes, microglia
What are the functions of oligodendrocytes (CNS) or Schann cells (PNS)?
-Produce myelin and facilitates its transmission
What are the functions of astrocytes?
-Enable homeostasis, physical barrier, re-uptake of neurotransmitters and support neurones
What are the functions of microglia?
-Immune cells of the brain, phagocytose dead cells and debris
What is the function of dendrites?
-Receive information and start action potential
What is the function of the soma?
-it’s a Cell body, contains organelles such as the nucleus
What is the function of the axon terminals?
-Communicate with other neurones or muscles
What is the function of the axons?
-Propagates action potential
What are the types of neurone in the PNS?
-Afferent (sensory) and efferent neurones
What does the afferent neurone do?
-Signals from PNS to CNS
What does the efferent neuron do?
-Motor neurons-CNS to muscles/skin autonomic neurons-CNS to smooth muscle/gland
What is the neurone in the CNS?
-Interneurons
What do interneurons do?
-connect the brain and spinal cord
What are the three types of neurotransmitter?
-Excitory, inhibitory, and neuromodulators
Give two examples of excitatory neurotransmitters ?
-glutamate and monoamines
Give 3 examples of inhibitory neurotransmitters?
-GABA, glycine and endorphins
Give 2 examples of neuro modulators ?
-neuropeptides and endocannabinoids
What protects the brain ?
-Cranium and meninges
What makes up the meninges ?
-Dura matter, arachnoid matter, Pia matter
What are the four regions of the spine ?
-Cervical, thoracic, lumbar, sacral
What forms the blood brain barrier ?
-Less permeable capillaries and endothelial cells lining the capillary walls with tight junctions between them
What happens in the frontal lobe?
-Reasoning, speech, planning, movement, problem solving
What happens in the occipital lobe?
-Visual processing
What happens in the temporal lobe?
-Perceptions and hearing
What happens in the parietal lobe ?
-Movement/ orientation recognition and stimuli perception
What does the brain stem do?
-Involuntary responses
What does the cerebellum do?
-Co-ordinates movement/balance
What does the cerebrum control?
-movement, speech, emotion, intelligence
What is the function of the autonomic nervous system?
-maintains internal environment controls visceral functions modulates endocrine function
What happens in ANS input (afferent)?
-Sensory neurons in peripheral organs to centres in hypothalamus and medulla
What happens in ANS output (efferent)?
-Sympathetic or parasympathetic nerves cause organ to innervate to cause moevemtn
What can a reflex arch link?
-Afferent and efferent ANS so brain does not have to get involved
What are visceral sensory neurons?
-Neurons that monitor internal changes and stretch in the visceral organs eg. stomach to inform brain of hunger
Where are visceral neurons found?
-Widely scattered around body but also running along with autonomic output nerves
What outputs for ANS nerves control?
-Smooth muscle, cardiac muscles and secretory glands
What neurons are present in a visceral reflex arc?
-visceral sensory and autonomic
How does a stimulus travel through a visceral reflex arc?
-Visceral fibre, dorsal root ganglion, CNS, preganglionic axon, visceral effector
What are the divisions of the ANS?
-Sympathetic and parasympathetic
What are the features of the sympathetic nervous system?
-Fight or flight
-Short term survival
-Increases energy availability, capacity and usage
What are the features of the parasympathetic nervous system?
-Rest and digest
-Long term survival
-Generally reduces energy availability, capacity and usage
What is an autonomic ganglion?
-Cell body terminal of the first neuron between the spinal cord and specific organ
What is the vagus nerve?
-A nerve that travels from the brain to the heart, stomach and other areas
Where do nerves originate in the SNS?
-Spinal cord
Where do the two neurons synapse in the SNS?
-Closer to the sympathetic ganglia
What are ionotropic receptors?
-Ligand-gated ion channels that have the binding site and channel combined, no second messenger and rapid response
What are metabotropic receptors?
-G-Protein coupled receptors where the binding site is not combined with a channel, has a second messenger and slower response
What is the effector neurotransmitter in the parasympathetic nervous system?
-Acetylcholine
What are the 2 acetylcholine receptors?
-Nicotinic and muscarinic
What is the effector in the sympathetic nervous system?
-Noradrenaline
What are adrenoceptors?
-GPCRs that respond to adrenaline and noradrenaline and have diverse actions depending on target
What is the somosensory cortex?
-Detects sensory events arising from different regions of the body. Located on the parietal lobe
What is the motor cortex?
-Issues response to stimuli in specific body part
What is an ascending tract?
-Relay information from the spinal cord to the sensory cortex
What is a descending tract?
-Relay information from the motor cortex to the spinal cord
What are the features of sensory neurones?
-Sense touch, pain, etc
-Relay information from spinal cord and brain
-Enter spine via Doral root
-Myelinated
What are the features of motor neurons?
-Relay nerve impulses from the spine to trigger contraction of skeletal muscle
-Exit spine via ventral root
-One alpha motor neuron from spinal cord to muscle
-Multi-polar and myelinated
What meets a neuromuscular junction?
-synapse of a somatic motor neuron and muscle fibres
What happens at the neuromuscular junction?
-Nerve impulse communicates with individual muscle
-Acetylcholine binds to and activates nicotinic acetylcholine receptor which is a ligand gated ion channel
What are the 3 types of muscle tissue?
-Skeletal, cardiac, smooth
What is skeletal muscle?
-Striated muscle that enables movement of limbs and other parts of the skeleton connected to the bone via tendons
What is the cardiac muscle?
-Striated muscle that has intrinsic pacemaker activity and pumps to aid circulation
What is a smooth muscle?
-Found around many hollow internal organs
-Functional syncytium
What is a functional syncytium?
-A single cell with multiple nuclei for rapid transfer of information
What muscles are part of the ANS?
-Cardiac
-Smooth
What is skeletal muscle made up of?
-Elongated muscle cells that have fused together and stretched lengthways
What are T-tubules?
-Invaginations of muscle fibre plasma membrane?
How is the sarcoplasmic reticulum different from ER?
-It is specialised to hold more Ca2+ ?
What are the 4 proteins involved in contraction?
-Myosin, actin, troponin, tropmyosin
How does a muscle contract?
-Myosin filaments slide along actin filaments. Z disks get closer together, H zone gets smaller then disappears as actin filaments overlap causing banding pattern
What happens in cross bridge cycling?
-ATP binds to myosin, myosin hydrolyses
-ATP and the energy released rotates the myosin head to the cocked position
-Ca2+ bind to troponin which changes position so actin and myosin can bind.
-Myosin releases ADP at the end of the power stroke
How does calcium act as the intracellular signal for contraction?
-Release of Acetylcholine at NMJ causes an electrical impulse in plasma membrane. This is carried to the cells interior by T tubules. The electrical impulse triggers the release of Ca2+ from the sarcoplasmic reticulum
Summarise the entire process of muscle contraction?
-Nerve action potential, nerve ending secretes ACH, end-plate potential, muscle action potential, T tubules depolarise and open Ca2+ channels, sarcoplasmic Ca2+ increases. Muscle fibre contracts, Ca2+ is pumped back into SR, muscle fibre relaxes
What neurotransmitter is released at the neuromuscular junction?
-Acetylcholine
How is acetylcholine transported across a synapse?
-ACh formed at the synaptic terminal, generated by choline acetyl transferase, packaged into vesicles, released into synaptic clef, broken down by achesterase, choline taken up
How does botox work?
-Stops vesicles fusing with presynaptic membrane
What are the 3 events during a muscle twitch?
-Latent period
-Contraction
-Relaxation
What happens in the latent period of a muscle twitch?
-Motor end plate depolarisation transmitted down T tubules
-Ca2+ channels open in SR
-Ca2+ binds to troponin revealing myosin binding site
What happens during contraction of a muscle twitch?
-Myosin binds to actin, moves, releases and reforms many times causing sacromeres to shorten
What happens during relaxation of a muscle twitch?
-Ca2+ actively transported back into SR
-Tropomyosin-troponin complex blocks myosin binding
-Muscle fibre lengthens passively
What is a motor unit?
-A motor neuron and its muscle fibres
Fine motor control requires ….. ratio of muscle fibres to nerve cells?
-smaller
What are the basic principles of motor neurons?
-All or nothing
-Threshold stimulus must be reached for contraction
-Recruitment, must have enough motor units for force required
Why does skeletal muscle contraction need ATP?
-Contraction (crossbridge forming )
-Relaxation (pump Ca2+)
-Restore Na+ and K+ levels after AP
Where does ATP for skeletal muscle contraction come from?
-Phosphocreatine
-Carbohydrates
What are the types of skeletal muscle fibre?
-Fast and slow twitch
What do antagonistic muscle group do?
-Move bones in opposite directions
-Contraction can pull on a bone, can not push bone away
What are the features of cardiac muscle?
-Muscle fibres are shorter and usually have one nucleus
-Connected by gap junctions and desmosomes
-Gap junctions allow quick transmission of action potential and contract in a wave-like pattern so that the heart can work as a pump
What specialised cells cause the heart to contract?
-Pacemakers (SAN)
What are the features of smooth muscle fibres?
-Lack striations
-Small cells with single nucleus
- have actin and myosin proteins
-Filaments occur in parallel
What are the similarities between smooth and skeletal muscle?
-Cross bridge movements initiated by increase in Ca2+ ions
-Force-sliding filaments
What are the differences between smooth and skeletal muscle?
-Smooth muscle contracts and relaxes more slowly
-Controlled by autonomic nervous system
-Ca2+ comes from outside the cells in smooth not tubules
-Smooth has no troponin in actin filaments, uses calmodulin
What receptor types does the sensory nervous system respond to?
-Mechanoreceptors, chemoreceptors, photoreceptors, termoreceptors, nociceptors
What are nociceptors?
-Respond to stimuli that result in sensation of pain
What broad categories can sense be split into?
-General senses and special sense
What is a sensory unit?
-A single afferent neuron and all its receptor endings
What is a simple receptor?
-Neurons with free nerve endings
What is a complex neural receptor?
-Nerve ending enclosed in connective tissue capsules
How is a special senses receptor different?
-Release neurotransmitters onto sensory neurons to initiate an action potential
What is a receptive field?
-Region of space where the presence of a stimulus will induce the production of a signal in the neuron
What are the features of somatosensory pathways?
-Linked to skeletal muscles, gives perception of touch, temp, body position, pain, process stimuli from receptors, responds voluntary and voluntary, project to cortex and cerebellum
What are the different receptors in the skin?
-Free nerve endings, merkel corpusle,meissners corpuscle, pacinian corpuscle and Ruffini corpuscle
Where do somatosensory pathways take the message?
-To the spinal cord and somatosensory cortex in the brain
What are the two afferent pathways to the brain?
-Dorsal column lemniscal
-Spinothalamic
What is the dorsal column lemniscal pathway for?
-Fine touch, vibration and position
What is the spinothalamic pathway for?
-Pain and temperature
What is a somatic reflex?
-An automatic, involuntary response that detects a stimulus and sends an impulse to the spinal cord which relays the information immediately back to the motor neurons
What are the five components to the reflex arc?
-Receptor, afferent neurone, integration centre, efferent neurone and effector organ
What type of receptors are muscle spindles?
-Proprioceptors
What are muscle spindles?
-Specialised muscle fibres surrounded by a capsule inside skeletal muscle that runs parallel to a muscle
What do proprioreceptors do?
-Sense muscle length and activate sensory neurones
When does a stretch reflex occur?
-When muscle proprioceptors detect the stretch ad tension of a muscle and send messages to the spinal cord to contract it
What is a stretch reflex?
1) stretching of muscle stimulates muscle spindles
2) activation of sensory neuron
3)Information processing at motor neuron
4) activation of motor neuron
5) contraction of muscle
What is the Golgi tendon organ?
-A proprioceptor in tendons
How do Golgi tendon organs control muscle contraction?
-Axons synapse onto inhibitory spinal interneurons which inhibit alpha motoneurons and reduce muscle contraction to regulate muscle tension until its in normal range
What does the cerebellum do?
-Controls balance, equilibrium and muscle co-ordination
What does the basal ganglia do?
-Initiation and sequencing of movement
