Nervous System Flashcards
What are two major subdivisions of the nervous system ?
Central nervous system (CNS) and peripheral nervous system (PNS)
What encompasses the CNS ?
Brain and spinal cord
What encompasses the PNS ?
All nervous tissue outside the CNS.
What are the brain and spinal cord contained in ?
The brain is contained in the cranial cavity of the skull. The spinal cord is within the vertebral cavity of the vertebral column.
What two basic cells are nervous tissue of both the CNS and the PNS comprised of ?
Neurons and glial cells.
What is another word for the cell body of neurons ?
Soma
What are processes ?
The extensions of the cell.
What is an axon ?
Process that all neurons. A fiber that connects neuron with its target.
Dendrite
Process that branches from the soma. Responsible for receiving most of the input from other neurons.
What is gray matter ?
Regions with many cell bodies and dendrites.
What is white matter.
Region of the brains with many axons.
Why is white matter white?
The axons are insulated by lipid rich axon substance, myelin.
What is a localized collection of neuron cell bodies in the CNS called ?
Nucleus
What is a cluster of cell bodies in the PNS called ?
Ganglion
What is a bundle of axons or fibers called in the CNS ?
Tract
What is a bundle of axons or fibers called in the PNS?
Nerve
What is sensation ?
Nervous system receives information about the environment around a person.
What is motor response ?
The response generated based on sensation.
Sensory functions
Regions of the brain which are responsible for sensation.
Motor functions
Regions of the brain responsible for response.
Integration
Region of the brain which is responsible for integration process; combining sensory perceptions and higher cognitive functions (memories, learning and emotion) to produce a response. The stimuli is compared to other stimuli (memory).
What does sensation involve ?
Stimulus - taste, smell, touch, sight and hearing.
What type of stimuli are the 5 senses ?
Taste and smell - chemical
Sight - light
Hearing - perception of sound which is physical
Touch - physical or mechanical
Are there more than the 5 senses in regards to stimuli ?
Yes, more sense can be found in the internal environment - stretching of organ wall or concentration of certain ions in the blood.
What does response entail in the nervous system ?
- based of stimuli
- nervous system can cause contraction of all three muscle types
- neurol control of the glands in the body (production and secretion)
How are responses divided in the body?
Voluntary (contraction of skeletal muscle) and involuntary (contraction of smooth muscle, regulation of cardiac muscle and activation of glands).
What governs involuntary responses in the nervous system ?
The automatic system.
What governs voluntary responses ?
The somatic nervous system.
What is the somatic nervous system ?
Responsible for conscious perception and voluntary motor response. Reflexes - skeletal muscle contractions.
What is autonomic nervous system ?
Responsible for involuntary control of the body - usually for homeostasis. Smooth and cardiac muscles, but also glandular. Role is to regulate the organ system.
What is the enteric nervous system ?
Responsible for controlling the smooth muscle and glandular tissue in your digestive system. Large part of the PNS not dependent on CNS.
What is the PNS divided into ?
- Somatic nervous system (SNS)
- Autonmic nervous system
What is the basis of communication in the nervous system ?
Action potential
What allows charged particles to move through the plasma membrane ?
Transmembrane proteins, specifically channel proteins
Does the Na+/K+ pump use energy ?
Yes, it uses ATP, so active transport as the Na+ and K+ move against their concentration gradient.
Why can channels interact with ions?
They have amino acids inside regions of the protein channel.
What will channels for cations (positive ions) have ?
The amino acids will have negatively charged amino acids.
What will channels for anions (negatively charged ions) have ?
They have positively charged side chains.
What is electrochemical exclusion?
The channel ision specific.
Size exclusion
Channels which are selective for size.
What is resting membrane potential ?
Steady state of the cell.
How is the dynamic process of the action potential maintained ?
Ion leakage and ion pumping.
What has to occur for a electrical signal to start ?
The membrane potential has to change.
What is depolarization ?
- channel opens for Na+ in the membrane
- Na+ moves into the cell due to the concentration gradient
- the voltage becomes less negative as the Na+ which are positively charged
- membrane potential moves towards zero
- the membrane potential will reach +30mV
Why does the voltage around the pores become positive during depolarization ?
The Na+ keeps moving into the cell even after the membrane potential reaches zero.
Repolarization
- as membrane potential reaches +30mV, the other potassium voltage gated channels open in the membrane
- K+ starts to leave the cell, taking a positive charge with it
- the membrane moves back towards -70mV
Hyperpolarization
- ## Occurs as the repolarization overshoots the -70mV resulting in it going below this number as potassium ions reach equilibrium with the membrane below -70mV (delay in K + channels closing)
What is the voltage change which occurs during depolarization ?
100mV, as -70mV to 30 mV
What type of Na+ channels are important for depolarization ?
-*some stimulus is needed
- ligand gated Na+ channel; opens when a neurotransmitter binds to it
- mechanically gated Na+ channel; opens when a physical stimulus affects a sensory receptor
- voltage gated Na+ channel
When does the voltage gated Na+ channel open ?
- help depolarization
- occurs due to a stimulus
What happens if depolarization does not reach -55mV or higher ?
If the threshold is not met then the action potential does not occur.
Do all action potentials peak at +30mV?
Yes, no action potential is bigger or smaller - all are the same.
What does a stronger stimuli do to action potentials?
Initiates multiple action potentials. NOT bigger action potentials.
What type of channels are depolarization and repolarization dependent on ?
Voltage gated Na+ channels and voltage gated K+ channel.
How many gates do voltage gated Na+ channels have and what do they do?
Two gates
Activation gate - opens when membrane crosses - -55 mV, when the threshold is reached
Inactivation gate -closes after a specific period of time
What happens to the two gates of the voltage gated Na+ channel when the cell is at rest ?
The activation gate is closed and the inactivation gate is open.
When do the activation and inactivation gate of the Na+ voltage gated channel open ?
- activation gate open when the threshold is reached
- peak of depolarization the inactivation gate closes
- during repolarization when no more Na+ needs to enter, when -55mV is reached again, the activation gate closes
- the inactivation gate opens
How many gates do the K+ voltage gated channel have and explain purpose ?
One channel, which is sensitive to -50mV. Opens slower than Na+ voltage gated channel. Opens when Na+ inflow has peaked and is being inactivated. Channel closes again when -50 mV reached during repolarization.
How long does the action potential process takes?
2 millisecond.
Can another action potential be initiated during an action potential ?
No
What time is it called when a nerve cell is unable to fire an action potential ?
Refractory period
How many phases of refractory period are there and what are they ?
2
- Absolute refractory potential
- Relative refractory potential
What happens during the absolute refractory period ?
- Another action potential will not start
- due to Na+ voltage gate, inactivation gate cannot reopen and activation gates are open
What is the relative refractory period ?
Period of time in which a second action potential can be initiated however is needs to be larger than the current actual potential. It occurs during the time when the voltage gated K+ channels are open after inactivated Na+ channels have returned to resting state. Occurs due to k+ ions flow out of the cell.
Where is the action potential propagated ?
Beginning of the axon, at a region called the initial segment.
What is the density like at the initial segment in regards to voltage gated Na+ channels and what does this mean for depolarization ?
High density, and rapid depolarization.
What does myelination do the propagation of an action potential ?
It is called saltatory conduction. It is faster because the action potential can jump from one node to the next.
How does the diameter of the axon influence the speed of conduction ?
Na+ depolarization occurs faster down a wide axon than a narrow axon. The concept is known as resistance.
What is propagation called in a unmyelinated axon?
Continuous conduction.
What are local changes in the membrane potential called ?
Graded potential
What are graded potentials usually associated with ?
Dendrites of the neuron
What determines the amount of change in the membrane potential ?
The size of the stimulus.
What are the two types of graded potentials ?
Depolarizing and hyperpolarizing.
What does a graded potential mean for a membrane at resting potential in relation to mV ?
It would be above -70mV or below -70mV.
What ions often cause depolarizing graded potentials and why those specific ions?
Na+ and Ca+ entering the cell. They usually have a high concentration outside the cell.
What ions often lead to a hyperpolarizing graded potential ?
Can be caused by K+ leaving the cell or Cl- entering the cell.
What is a postsynaptic potential (PSP)?
The graded potential in the dendrites of a neuron that is receiving synapses from other cells.
Can be depolarizing or repolarizing.
What is depolarizing in the postsynaptic potential called ?
Excitatory postsynaptic potential (EPSP) - membrane potential moves towards threshold.
What is hyperpolarization called in the postsynaptic potential ?
Inhibitory postsynaptic potential (IPSP) - causes the membrane potential to move away from threshold.
What is summation ?
Graded potentials result in small changes in relation to depolarization and hyperpolarization being added together.
Spatial summation
Associating the activity of multiple inputs to a neuron with each other.
Temporal summation
Multiple action potentials from a single cell resulting int a significant change in the membrane potential.
What are the two types of connections between electrically active cells?
Chemical synapses and electrical synapses.
What is chemical synapses ?
A chemical signal - neurotransmitter- is released from on cell and its affects the other cell.
What is a electrical synapses ?
Ther is a direction connection between two cells so that ions can pass directly from one cell to the next.
What happens to a cell joined to a cell which is depolarized in an electrical synapse ?
The joined cell also depolarizes as the ions pass between the cells.
All synapses have what common characteristics?
- Presynaptic elements
- Neurotransmitters (packaged in vesicles)
- Synaptic cleft
- Receptor proteins
- Postsynaptic element
- Neurotransmitter elimination or re - uptake
PNSRPN
Explain neurotransmitter release
- Action potential reaches the axon terminals
- Voltage gated Ca2+ channels in the membrane of the synaptic end bulb open
- Concentration of Ca2+ increase inside the end bulb
- Ca2+ associates with proteins in the outer surface of the neurotransmitter vesicles.
- Ca2+ facilitates the merging of the vesicles with the pre-synaptic membrane so that the neurotransmitter is released through exocytosis into the small gap between the cells (synaptic cleft).
Once in the synaptic cleft, the neurotransmitter diffuses the short distances to the postsynaptic membrane which can interact with neurotransmitter receptors.
Are receptors for neurotransmitters specific ?
Yes
Brain stem
Comprised of both midbrain and hindbrain.
Connects brain to spinal cord.
What part of the nervous system is the sensory (afferent) and motor (efferent) systems part of ?
PNS
What are the subdivisions of the autonomic nervous system ?
Sympathetic nervous system and the parasympathetic nervous system
Describe the sympathetic nervous system
Part of autonomic response
‘fight or flight’ response
- occurs when body is under stress
Stress response includes
- increased heart rate and respiration rate
- decreases the activity of the organs that are not required during stress, including digestion
Describe the parasympathetic nervous system
Part of autonomic nervous system
- Controls ‘rest and digestion’ body activities
- relaxed heart rate and respiration rate
- regulating digestion
What are examples of visceral functions which the autonomic nervous system controls ?
- Heart rate
- Rate of respiration
- Digestion
What are the key functions of the brain
- Cognition
- Sensory perception
- Motor control
- Emotions
- Memory
- Autonomic functions
How many lobes are the cerebral cortex, the covering of the outer surface of the cerebral hemispheres, divided into ?
4 lobes
Name the lobes of the cerebral cortex
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
What is the frontal lobe involved in?
- motor function
- problem solving
- spontaneity
- memory
- language
- initiation
- judgement
- impulse control
- social and sexual behavior
What is the parietal lobe involved in ?
- responsible for processing sensory information
- spatial sense
- main sensory area of tough
What is the temporal lobe involved in ?
- Processing auditory information
- Memory
- Integration of visual and auditory information
What is the occipital lobe involved in ?
- Primarily responsible for visual processing ?
Location of the lobes in the cerebral cortex
Frontal - front
Parietal - top mid
Temporal - bottom mid
Occipital - back, above cerebellum
What does the cerebellum do ?
- Coordinates muscle movements
- Coordination and balance
Hippocampus
Memories
Thalamus
- Relays info body to brain
- Information from skin and pain
Brain stem
- Oldest part
- relay control center automatic functions; breathing, HR, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting and swallowing
- cranial nerves originate in the brain stem
Hypothalamus
- Master control of the autonomic system
- works with the pituitary system
- Controls behaviors such as hunger, sleep and sexual response
- regulates body temp, blood pressure, emotions and secretion of hormones.
Limbic system
- ‘emotional brain’
- controls complex emotional behavior involving different areas of the brain.
Includes the amygdala (rage and aggression), hippocampus (memories) and hypothalamus (regulates emotions).
Amygdala
Emotions, part of limbic system
Photoreceptors, location and function
Retina and detect light and colour
Mechanoreceptors, location and function
Skin, muscles and inner ear
Respond to mechanical pressure or distortion
- touch, pressure, vibration and hearing loss
Thermoreceptors, location and function
Skin and internal organs
Detect changes in temperature
Chemoreceptors, location and function
Muscles, tendons and joints
Provide information about body position and movement
Baroreceptors, location and function
Blood vessels, heart and kidney
Detect changes in blood pressure
Stretch receptors, location and function
Muscle, lung and bladder
Respond to stretching of tissues, involved in muscle length and visceral organs distension.
What does the corpus callosum do ?
Enables the two hemispheres to communicate.
What does the pineal gland ?
- a secretory circumventricular organ of the brain - fenestrate capillaries - pores
- modulates and secrete melatonin
- hormones influence other endocrine glands
What does the cerebellum do ?
- regulates posture and balance
- smooths and coordinates contractions of skeletal muscles
What does the medulla Oblongata do ?
- sensory and motor tracts
- regulates heart beat, blood vessels diameter
- regulates breathing
- vomiting, swallowing, sneezing and coughing
What do the pons do ?
- Sensory and motor tract
- helps control breathing
What does the midbrain do ?
- sensory and motor tract
- coordinates movement of head and eyes
- contributes to control of movement
Pituitary gland
- regulation of metabolism, growth, sexual maturation, reproduction, blood pressure, breastfeeding, immune system and other physical functions.
Hypothalamus
- Controls and integrates activities of the autonomic immune system
- produces hormones, inhibits hormones
- regulates emotional and behavioral patterns
- controls body temperature
- Regulates eating and drinking habits
Thalamus
- relays most of sensory info to cerebral cortex
- contributes to motor function by transmitting info from cerebellum and basal nuclei and cerebral cortex
- role in maintenance of consciousness
What does the limbic system do ?
Involved in emotion and memory
What does the amygdala do ?
- part of limbic system
- regulates emotions
- plays a role in memory consolidation
What does the Hippocampus do ?
Associated with learning and memory
Vision (Sight)
The eyes contain photoreceptor cells in the retina that detect light and color.
Light entering the eye is focused by the lens onto the retina, where it forms an inverted image.
Photoreceptor cells (rods and cones) in the retina convert light stimuli into electrical signals.
The optic nerve carries these signals to the visual cortex in the brain for processing and interpretation.
Hearing (Audition)
The ears contain specialized structures, including the cochlea, that convert sound waves into electrical signals.
Sound waves enter the ear canal and cause vibrations in the eardrum.
These vibrations are transmitted through the middle ear bones to the cochlea, where hair cells convert the mechanical vibrations into electrical signals.
The auditory nerve carries these signals to the auditory cortex in the brain for processing and interpretation.
Smell (Olfaction)
Olfactory receptors in the nose detect chemical molecules in the air.
These receptors send signals to the olfactory bulb, which processes the information.
The olfactory nerve carries the signals to the olfactory cortex in the brain, where they are interpreted as different smells.
Taste (Gustation)
Taste buds on the tongue detect different chemical compounds in food.
Taste receptor cells send signals to the gustatory cortex in the brain for interpretation.
Smell and taste often work together to create the perception of flavor.
Touch (Somatosensation)
The skin contains various types of receptors, including mechanoreceptors, thermoreceptors, and nociceptors.
Mechanoreceptors detect pressure, vibration, and touch, while thermoreceptors detect temperature, and nociceptors detect pain.
Signals from these receptors are transmitted through nerve fibers to the somatosensory cortex for processing.
Proprioception (Body Position and Movement)
Proprioceptors in muscles, tendons, and joints provide information about the body’s position and movement.
This information is crucial for coordinating and controlling voluntary movements.
Neurotransmitter removal from synapse
- Diffusion
- Digestive enzymes
- Re uptake
