The Nervous Systems Flashcards
ACTION POTENTIAL
• A chain reaction reversing voltage rapidly and then restoring it
• Done by ion channels with gates regulating the passage
→ Concentration force and electrostatic force dicide direction of diffusion through channels
→ Leak channels = randomly open and close cause ion leakage
→ Voltage-gated channels = their gates open in response to change in membrane potential
• 6 events: receptor potential, the threshold, Depolarization, Repolarization, Hyperpolarization, and refraction period
Receptor potential
Stimuli opens sodium-ion (Na2+) channels → ions diffuse into the cell due to concentration and electrostatic force → membrane potential change
The Threshold
• -55 mV must be reached for action potential (nerve impulse) to be generated
• If stimuli big enough → threshold reached → voltage-gated channels open → sodium-ions rush in
DEPOLARIZATION
• Start of action potential
• As sodium-ions continue to diffuse in → membrane potential gets positive → when ca 30 mV is reached sodium-ion channels close
• Inside of cell is now positive and outsid cell is negative
REPORALIZATION
• Second step in events of action potential
• 30 mV reached → potassium-ion (K+) channels open (at same time as sodium-ion channels close) → potassium-ions diffuse out due to concentration and electrostatic force → membrane potential decreases to negative
HYPERPOLARIZATION
• Last step in the events of action potential
• As potassium-ions continue to diffuse out → membrane potential reach -80 mV → potasium-ion channels close
Refraction period
• Active pumps, sodium-potassium pumps, sending sodium-ions out of cell and potassium-ions into cell → resting membrane potential restored
• The neuron is unable to generate new action potential during this time (until -70 mV is restored in membrane)
NEURON - function
• Communication between different body parts - signals are sent all the time
• Communication between the body and it’s environment - senses detect changes in environment → adjustments if needed
THE SYNAPSE
• The place where neuron meet another neuron or other cell; ALSO name of the process of chemical communication between cells
• Presynaptic neuron = neuron sending signal (with the action potential)
• Postsynaptic neuron = neuron recieving the signal
• Between pre- and postsynaptic neuron = synaptic cleft (action potential cannot cross, thus chemical communication needed)
Events of synapse - PRESYNAPTIC NEURON
1. Action potential reach synaptic and bulb (end of a terminal of presynaptic axon) → depolarization
2. Voltage-gated calcium-ion channels open in the membrane of synaptic end bulb → Ca2+ diffuse into end bulb due to concentration → increased concentration of Ca2+ inside
3. Ca2+ bind to proteins → exocytosis of existing synaptic vesicles containg transmittor molecules → drain transmittors into the synaptic left
Events of synapse - SYNAPTIC CLEFT → POSTSYNAPTIC NERON/CELL
1. Transmittors diffuse across synaptic cleft → bind to transmitfor receptors in the postsynaptic dendrite’s membrane
2. lon channels open in dendrite of postsynaptic neuron → certain ions diffuse into the cell
3. Membrane potential changes in postsynaptic cell → depolarization or hyperpolarization
Postsynaptic potentials
• Excitatory postsynaptic potential = if sodium- or calcium-ion channels open in dendrite as result of the synapse → depolarization → action potential is transferred from pre- to postsynaptic neuron
• Inhibitatory postsynaptic potential = if potassium- or clorine-ion channels open → hyperpolarization → action potential is not transferred
(NEURO)TRANSMITTORS
• Actylcholine (ACh): exitatory (inhibitatory in parasympathetic); released by many PNS and some CNS neurons → binds to nicotineic and muscarinic receptors
• Noradrenaline, adrenaline: binds to alpha or beta receptors
• Serotonin: involved in mood, apitite, sleep, and temperature regulation; binds to 5HT receptors
• Dopamine: active during emotional responses, addiction, and plessure; binds to D-receptors
• Glutamate: exitatory amino acid
• GABBA: inhibitatory amino acid; present in antianxiety medications
ACTION POTENTIAL - Conduction
• The spread of a action potential throughout an axon
• It’s the depolarization that travels → when one segment of the axon has been depolarized, the next segment is triggered as the previous one gets repolarized
• Continuos conduction = impulse throughout unmyelinated axon
• Saltatory conduction = impulse throughout myelinated axon: *voltage pulse go through myelin sheath → action potential starts in next node
Neurons in nervous systems - divisions
• Neurons present in groups, mixing myelinated and unmyelinated neurons → forms two tissues: Gray matter = cell bodies; White matter = axons
• Afferent neuron = neuron sending signals into CNS
• Efferent neuron = neuron sending signals out of CNS
• Interneuron = neuron in between other neurons, connecting or sending signals in between them
Central Nervous System = CNS
• Includes the brain and spinal cord
• Processes sensory information and is the source of thoughts and emotions
• Gray matter: nuclei
• White matter: tracts
• Glial Cells: Astrocytes, Oligodendrocytes, Epidymal cells, Microglia
MENINGES
• Connective tissue around CNS:
Epidural space (only in the spinal canal)
• Dura mater
subdural space
• Arachnoid mater
subarachnoid space
• Pia mater
CerebroSpinal Fluid = CSF
• Produced in choroid plexus → in the ventricles of the brain
• Protection of CNS and exchange nutrients and wastes between CNS and blood
• Made from blood plasma
VENTRICULAR SYSTEM
• Four ventricles: 2 lateral ventricles, 1 third ventricle, and 1 fourth ventricle
• CSF flows from the ventricles into the central canal and the subarachnoid space
• CSF reabsorbs into blood through Arachnoid villi = small projections of arachnoid mater into dura mater
Blood-Brain Barrier
• Tightly sealed capillaries protecting brain cells by preventing passage of harmful substances and pathogens
• Assisted by Astrocytes
• Lipid-soluble substances can pass (O2, CO2 ex.)
Vascularistation of the brain → blood supply
• Circalus arteriosus cerebri = circulation of arteries supplying brain with oxygenized blood
• Aorta → (Brachiocephalic trunk if right side) → Common carotid artery (dx./sin.) → Internal carotid artery (dx./sin.) → Circulus arteriosus cerebri
• Aorta →(Brachiocephalic artery if right side) → Subclavian artery (dx./sin.) → VertebraI artery (dx./sin.) → Basilar artery (dx. and sin. vertebraI artery joins) → Circalus arteriosus cerebri
THE BRAIN
• Parts:Cerebrum, Cerabellum, Diencephalon, Masencephalon, Pons, and Medulla Oblongata
• Protected by cranium and meninges
• Requires 20% of the body’s oxygen supply
CEREBRUM - Structure
• Largest part of the brain
• Outer surface: folded gray matter = cerebral cortex
• Internal region: white matter
• 3 masses of gray matter within white matter = basal nuclei: regulate muscle tone, initiate, and terminate movements
CEREBRUM - Cerebral cortex
• Folds = gyri; deep/shallow grooves = fissures/sulci
• Longitudinal fissure → divides cerebrum → 2 cerebral hemispheres (left/right), connected by corpus callosum (white matter)
• Eeach hemisphere → 4 lobes: frontal, parietal, temporal, and occipital
• Brocca’s area = speach center → left frontal lobe; Wernick’s area = center for interpretation of speach → left temporal lobe
• Central sulcus: seperates frontal and parietal lobe
• Pre-/postcentral gyrus = anterior/posterior of central sulcus
DIENCEPHALON - Structure
• Between brain stem and cerebrum
•Internal capsule = ascending and descending tracts
• Thalamus = divided into left/right
• Hypothalamus = below thalamus
• Pituitary gland = attached to hypotheticalmus
Thalamas
• Information relay station: sensory and motor signals → cerebral cortex for interpretation
• Transmits nerve impulses between different areas of the cerebrum
• Plays a role for consciousness
Hypothalamus
• Controls ANS (autonomic nervous system)
• “Master” endocrine gland → controls pituitary gland’s production of hormones
• Regulates emotions together with the limpic system
• Regulates eating/drinking and circadian rythms (biological clock)
• Controls body temperature
Pituitary gland (hypophysis)
• Posterior pituitary = neurohypophysis
• Anterior pituitary = adenohypophysis
CEREBELLUM
• 2 cerebellar hemispheres
• Connected to the brain stem by cerebellar peduncles = bundels of axons
• Cerebellar cortex (gray matter) with white matter under
• Regulates and helps our balance and coordination
BRAIN STEM - Structure
• Between diencephalon and the spinal cord
• 12 pairs of cranial nerves goes through
• Reticular formation extends through → region where gray and white matter intermingle
• 3 parts: mesencphalon, pons, medulla oblongata
Mesencephalon
• Connects pons to diencephalon
• Cerebral peduncles = axons of motor neurons conducting impulses from cerebral to spinal cord
• Substantia nigra = part of nuclei; big role in motor functions
• Collieulli = 4 rounded “hills” of nuclei in the front; 2 sup. for vision, 2 inf. for hearing
Pons
• Middle of brain stem
• A bridge → connects parts of the brain through bundles of axons
• Some axon bundles are part of ascending sensory and descending motor tracts
• Nuclei pass on signals for voluntary movements from cerebra cortex → cerebellum
Medulla Oblongata
• A continuation of the spinal cord
• White matter consists of sensory (ascending) and motor (descending) tracts → exdend between spinal to parts of the brain
• Several nuclei, 2 major forming: cardiovascular center = regulates heart rate/force and diameter of blood vessels, and respiratory center = regulates basic breathing rythm
THE SPINAL CORD - Structure
• Located within the vertebral canal segmented in 31 segments
• Extends from medulla → lower lumbar level
• Central canal in the middle → filled with CSF
• Gray matter divided into horns
• Around gray matter are white matter consisting of different tracts → motor (descending) and sensory (ascending) tracts
THE SPINAL CORD - a segment
• Dorsal horns = cell bodies and axons of interneurons and axons of afferent (sensory) neurons
• Ventral horns = cell bodies of somatic motor (efferent) neurons → contraction of skeletal muscle
• Spinal nerves = pathways for communication between spinal cord and body parts
• Roots = bundles of axons connecting spinaI nerve to segment of the cord
• Dorsal root = afferent signals with a swelling of sensory neurons’ cell bodies → dorsal root ganglion
• Ventral root = efferent signals
THE SPINAL CORD - Physiology
Afferen (sensory) signal enters through dorsal root and it’s ganglion → the signal synaps in the gray matter with an efterent neuron → efterent signal sent out from the ventral root
Peripheral Nervous System - PNS
• Nervous tissue outside of CNS
• Ganglions = gray matter
• Nerves = white matter
NERVES - Structure
• Fasicles = bundles of axons
• Endoneurium = connective tissue with blood vessels around axons in a fasicle
• Epineurium = encloses each fasicle
• Perineurium = space between fasicles
Spinal nerves
• Belong to PNS
• Connect receptors, muscles, and glands to CNS
• 31 pairs named after the vertebraI column they emerge from
• IntervertebraI foramen = holes between vertebrates where nerves emerge through
Cranial nerves
2 Optic nerve → vision
3 Oculomotor nerve → movements of eyeball the upper eyelid
5 Trigeminal nerve → somatic sensations and chewing
7 Facial nerve → taste, facial expressions, secretion of tears and saliva, and somatic senses
8 Vestibulochlear nerve = hearing and balance
9 Glossopharyngeal nerve = taste, swallowing, speech, saliva, and monitor gas pressure in blood
10 Vagus nerve → swallowing, coughing, voice, slowing heart rate, secretion of digestive fluid
PLEXUSES
• Networks of nerves mingling together in the body
• Nerves emerge from these networks (plexuses)
• 4 major plexuses: Cervical, brachial, lumbar, sacral
• Nerves extending from thoracic level do not form plexuses → intercostal nerves supply costal- and abdominal muscles, and the skin of chest and back
Dermatomes
• Refers to skin areas
• Tells where different nerves are located
• Big nerves → lot of axons → more motor units → fine motoric
