The Nervous Systems

Question 1

ACTION POTENTIAL

Answer 1

• 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

Question 2

Receptor potential

Answer 2

Stimuli opens sodium-ion (Na2+) channels → ions diffuse into the cell due to concentration and electrostatic force → membrane potential change

Question 3

The Threshold

Answer 3

• -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

Question 4

DEPOLARIZATION

Answer 4

• 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

Question 5

REPORALIZATION

Answer 5

• 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

Question 6

HYPERPOLARIZATION

Answer 6

• Last step in the events of action potential
• As potassium-ions continue to diffuse out → membrane potential reach -80 mV → potasium-ion channels close

Question 7

Refraction period

Answer 7

• 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)

Question 8

NEURON - function

Answer 8

• 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

Question 9

THE SYNAPSE

Answer 9

• 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)

Question 10

Events of synapse - PRESYNAPTIC NEURON

Answer 10

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

Question 11

Events of synapse - SYNAPTIC CLEFT → POSTSYNAPTIC NERON/CELL

Answer 11

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

Question 12

Postsynaptic potentials

Answer 12

• 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

Question 13

(NEURO)TRANSMITTORS

Answer 13

• 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

Question 14

ACTION POTENTIAL - Conduction

Answer 14

• 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

Question 15

Neurons in nervous systems - divisions

Answer 15

• 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

Question 16

Central Nervous System = CNS

Answer 16

• 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

Question 17

MENINGES

Answer 17

• Connective tissue around CNS:
Epidural space (only in the spinal canal)
• Dura mater
subdural space
• Arachnoid mater
subarachnoid space
• Pia mater

Question 18

CerebroSpinal Fluid = CSF

Answer 18

• 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

Question 19

VENTRICULAR SYSTEM

Answer 19

• 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

Question 20

Blood-Brain Barrier

Answer 20

• 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.)

Question 21

Vascularistation of the brain → blood supply

Answer 21

• 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

Question 22

THE BRAIN

Answer 22

• Parts:Cerebrum, Cerabellum, Diencephalon, Masencephalon, Pons, and Medulla Oblongata
• Protected by cranium and meninges
• Requires 20% of the body’s oxygen supply

Question 23

CEREBRUM - Structure

Answer 23

• 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

Question 24

CEREBRUM - Cerebral cortex

Answer 24

• 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

Question 25

DIENCEPHALON - Structure

Answer 25

• Between brain stem and cerebrum •**Internal capsule** = ascending and descending tracts • **Thalamus** = divided into left/right • **Hypothalamus** = below thalamus • **Pituitary gland** = attached to hypotheticalmus

Question 26

Thalamas

Answer 26

• 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

Question 27

Hypothalamus

Answer 27

• 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

Question 28

Pituitary gland (hypophysis)

Answer 28

• Posterior pituitary = neurohypophysis • Anterior pituitary = adenohypophysis

Question 29

CEREBELLUM

Answer 29

• 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

Question 30

BRAIN STEM - Structure

Answer 30

• 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**

Question 31

Mesencephalon

Answer 31

• 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

Question 32

Pons

Answer 32

• 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

Question 33

Medulla Oblongata

Answer 33

• 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*

Question 34

THE SPINAL CORD - Structure

Answer 34

• 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

Question 35

THE SPINAL CORD - a segment

Answer 35

• **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

Question 36

THE SPINAL CORD - Physiology

Answer 36

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*

Question 37

Peripheral Nervous System - PNS

Answer 37

• Nervous tissue outside of CNS • **Ganglions** = gray matter • **Nerves** = white matter

Question 38

NERVES - Structure

Answer 38

• **Fasicles** = bundles of axons • **Endoneurium** = connective tissue with blood vessels around axons in a fasicle • **Epineurium** = encloses each fasicle • **Perineurium** = space between fasicles

Question 39

Spinal nerves

Answer 39

• 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

Question 40

Cranial nerves

Answer 40

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

Question 41

PLEXUSES

Answer 41

• 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

Question 42

Dermatomes

Answer 42

• Refers to **skin areas** • Tells where different nerves are located • Big nerves → lot of axons → more *motor units* → **fine motoric**