Week 6- Nervous System Flashcards
What is the structure of a neuron?
1) Has cell body
2) Contains dendrites that composes impulses towards the cell body (short, branched fibres)
3) Contains axons that send impulses away from the cell body. (Long, single process)
What are the three different neurons?
1) Multipolar neuron
2) Bipolar neuron
3) Unipolar neuron
What is the function of the neuroglia?
1) Support
2) Segregate/ insulate neurons
3) Protection
4) Promotes health and growth
What is the myelinated neuron?
Cells that surround axons with layers of plasma membrane (lipid & protein)
what is the function of the myelin shealth?
Electrically insulate axon that increase the speed of nerve impulse conduction.
What is the ganglion?
A collection of cell bodies of the neurons outside the CNS.
What is the nerve?
- Bundle of neuron fibres outside the CNS.
- A collection of many axons.
What is grey matter?
- Grey matter is the nerve cell bodies inside the CNS.
What is white matter?
Neuron fibres within CNS
What is tract?
- A bundle of neuron fibres in the CNS.
- Runs from brain-spinal cord (vice versa)
- White in colour due to myelin sheaths covering the axons.
Voluntary contration decisions happens where?
The brain
AKA CNS
The decisions for voluntary movements are transferred to the muscle from what?
Motor neurons
(Brain-motor neurons)
What is the organization of the peripheral nervous system?
-Peripheral Nervous system
(divides into 2 categories)
- Somatic/automic nervous systems
(automic nervous system divides to 2 sections)
- Sympathetic division / parasympathetic division
What is the different of afferent and efferent nerves in the PNS?
- Afferent nerves carry electrical impulses from receptors in the body to the CNS.
- Efferent nerves carry electrical impulses from the CNS to the muscles and glands.
What is the function of the somatic nervous system?
- Controls voluntary movements
- Deals with the parts of the body that you can move voluntarily
What is the function of the automic nervous system?
- Regulates the functions of internal organs such as the heart, stomach, intestines and some muscles.
- Unaware of the automic nervous system because it’s involuntary.
Automic nervous system facts?
- Divided into sympathetic and parasympathetic divisions
- Many organs receive efferent neurons from both these divisions
- divisions are often antagonistic
- Neurotransmitters secreted by nerve ending usually different between the two divisions
- Hypothalamus – control centre
What is the difference of sympathetic/parasympathetic ?
- Sympathetic divison is arousing
- Parasympathetic division is calming
What is the sympathetic and parasympathetic division for eyes?
- Sympathetic = pupils dilate
- Parasympathetic = Pupils contract
Sympathetic/parasympathetic division for salvation
Sympathetic- Decreases
Parasympathetic- Increases
Sympathetic/Parasympathetic division for skin
Sympathetic - Perspires
Parasympathetic - Dries
Sympathetic/Parasympathetic division with Respiration
Sympathetic- Increases
Parasympathetic- Decreases
Sympathetic/Parasympathetic division for the heart
Sympathetic- Accelerates
Parasympathetic- Slows
Sympathetic/Parasympathetic division for Digestion
Sympathetic- Inhibits
Parasympathetic- Activates
Sympathetic/Parasympathetic division for Adrenal Glands
Sympathetic- Secretes stress hormones
Parasypathetic- Decrease secretion of stress hormones
Sympathetic/Parasympathetic division for Immune system functioning
Sympathetic- Reduced
Parasympathetic- Enhanced
When does the action potential occur?
When a neuron sends information down an axon, away from the body.
Resting membrane potential facts
- Present in all cells
- Inside of the cell membrane is negative compared to the outside
- Has large quantities of negatively charged protein molecules inside the cell that cannot leak out.
What are the three key factors for the resting membrane potential?
1) Sodium / potassium pump
2) The prescense of leaky potassium channels
3) Large quantities of negativelycharged protein molecules inside the cell that cannot leak outside
Leaky potassium ion channels facts
- More of them inside than outside of cell
- potassium (k+) leak channels that lets potassium leave the cell body by facilitated diffusion through concentration gradient
- Exit of potassium carries a positive charge to outside of cell
- Contributes to the inside of the cell being more negative than the outside
What are the types of plasma membrane ion channels?
1) Passive / leakage channels- always open
2) Ligand- gated channels- open with a binding of a specific neurotransmitter
3) Mechanicallly- gated channels- opens/closes with stimulation (vibration, touch, etc.)
4) Volted- gated channels- Open/closes in response to membrane potential
What is the resting state of the neuron?
Phase 1
- All voltage-gated channels are closed from NA+/K+ to pass through.
- The axon plasma membrane is at its resting membrane potential.
AKA: equal buildup of negative and positive ions in inside/outside of membrane surface.
What is th depolarizing stage of the neuron?
phase 2
- NA+ channel activation gates open when membrane potential of axon reaches threshold.
- When the na+ rushed through this channel, the inside of the cell becomes depolarize
What is propagation?
When an action potential occurs at one side of the membrane and then follows all the way down to the end (like a chain reaction)
What is the repolarization phase of the neuron?
phase 3
- Happens when about 30mV of action potential is reached
- The NA+ gates close and the K+ gates open.
- The membrane starts to become polarized again due to k+ resurfacing to outside of cell, leaving negative charge inside cell.
What is phase 4 of neuron?
- Repolarization phase continues
- As more k+ ions leaves the inside membrane, the negative charge becomes more domanint inside, restoring resting membrane potential.
- Na+ channel inactivation gates open.
- Returns back to resting state when k+ gates close
Why does action potential only go one way?
- Due to refractory period.
- When the sodium channel gates close, they “reset”, resulting in no other action potential being able to generate.
- As the sodium is depolarizing throughout the membrane, the sodium voltage gates are still being reset and will not open
AKA reason for action potential being generated in one direction.
What is the reason for the myelin sheath ?
To make the action potential travel through the axon faster.
- Acts as a insulator fron ions crossing the membrane.
- Ions can cross through the nodes of the ranvier.
- Causing saltatory conduction (faster movement)
What is the synaptic transmission?
- The realeasing of nerve pulses from the axon bulbs of one neuron to another.
What is the synapse transmission process?
1) Nerve impulses arrive at axon bulbs
2) Volted gated calcium (Ca2+) gates open, rushing Ca2+ into the bulb
3) Ca2+ causes vesicles to move to presynaptic membrane, undergoing exocytosis, releasing neurotransmitters into synaptic cleft
4) Neurotransmitters diffuse across clefts
5) Neurotransmitters fit into receptors of ligand-gated Na+ gates, opening them
6) Na+ rushes into cell, causing action potential to develop
What are neurotransmitters?
Type of chemical messenger which transmits signals across a chemical synapse
What is The role of neurotransmitters in conducting a nerve impulse across a synapse?
- can be inhibitory or excitatory, depending upon the area of the nervous system it is used in
- Whether it is inhibitory or excitatory depends upon what type of gates it opens
- it is used by the neurons that are responsible for that function
Acetylcholine neurotransmitters facts
- Released at many synapses in the brain and peripheral nervous systems
- Released at the neuromuscular junction
- Can have either excitatory or inhibitory action, depending upon which part of the nervous system is using it
- Its effects are terminated through the action of acetylcholinesterase
What are the three types of neurotransmitters?
1) Norepinephrine
2) Dopamine
3) Serotonin
Peptides neurotransmitters facts
- Include endorphin and enkephalins
- Act as natural opiates, reducing pain perception
- Bind to the same receptors as opiates and morphine
What is the brain protected by?
1) . Bone
2) Meninges
3) cerebrospinal fluids
How are harmful substances shielded from the brain?
Blood- brain barriers
What are blood brain barriers?
- Protects that brain from harmful substances and pathogens by preventing the passage from blood into brain tissue
- No spaces between the cells of capillary walls – nothing can leak between
- Also a thick basement membrane around the capillaries
- Anything that goes across must go through cells, not between
What are meninges?
- Three connective tissues that lie external to the CNS
What are the three types if meninges?
1) Dura mater
2) Arachnoid mater
3) Pia mater
What are the functions of the meninges?
1) Protect/cover the CNS
2) Protect blood vessels and enclose venous sinuses
3) Contain cerebrospinal fluid (CSF)
4) Forms partitions within the skull
What are ventricles of the human brain?
4 Cavities within the brain that contain cerebral spinal fluid (CSF)
- Cerebrospinal fluid lies in the subarachnoid space, Within the ventricles, In the central spinal canal
What is Cerebrospinal Fluid (CSF) and function?
- Watery solution with different solute concentrations
- Function:
1) Forms a liquid cushion to give buoyancy to the CNS organs
2) Prevents the brain from crushing under its own weight
3) Protects the CNS from blows and other trauma
4) Nourishes the brain and carries chemical signals throughout it
What is the cerebrum/ functions?
- the principal and most anterior part of the brain in vertebrates, located in the front area of the skull and consisting of two hemispheres, left and right, separated by a fissure.
- Function:
1) Perception or interpretation of sensory impulses
2) Emotional and intellectual processes
3) Control of motor movements
What is the Diencephalon?
- Central core of the forebrain
- Consists of 2 major structure:
1) Thalamus
2) Hypothalamus - Encloses the third ventricle
What are the thalamuc functions?
- Afferent impulses from all senses converge and synapse in the thalamus
- Impulses of similar function are “sorted out,” edited, and relayed as a group
- All inputs ascending to the cerebral cortex pass through the thalamus
- Plays a key role in mediating some sensation
(e. g. pain, temperature, light touch and pressure) - Role in limbic system – pain and pleasure interpretation
What is the hypothalamus?
- Located below the thalamus
- Principle intermediary between nervous and endocrine systems
-
What is the function of the hypothalamus?
Main visceral control centre of the body through regulations of: – Autonomic nervous system
– Heart rate
– Water balance
– Thirst
– Food movement through GIT
– Thermoregulation
– sleep
What is the Infundibulum?
stalk of the hypothalamus: connects to the pituitary gland
What is the brain stem / functions?
- the central trunk of the mammalian brain consisting of:
1) midbrain
2) pons
3) medulla oblongata - continues downward to form the spinal cord
- Function:
1) Controls automatic behaviors necessary for survival
2) Provides the pathway for tracts between higher and lower brain centres
What is the midbrain/ functions?
- Located between the diencephalon and the pons
- Function: Reflex center for head and eye movements in response to sight and sounds
What are pons/ functions?
- Bulging brain stem region between the midbrain and the medulla oblongata
- Functions:
1) Also forms bridge between cerebellum and brain stem
2) All sensory and motor fibres pass through the pons
3) Pneumotaxic centre regulates respiration
What is the medula oblongata/ functions?
- Most inferior part of the brain stem
Functions:
1) Cardiac centre – regulates heart rate
2) Respiratory centre- regulates rate and depth of breathing
3) Vasomotor centre – regulates blood pressure
4) Regulates swallowing, sneezing, vomiting
What is the cerebellum/ functions?
- the part of the brain at the back of the skull in vertebrates
- Functions:
1) Provides precise timing and appropriate patterns of skeletal muscle contraction
2) Maintains posture
3) Maintains equilibrium using sensory input from inner ear
What is the spinal cord?
- a series of 31 segments, each giving rise to a pair of spinal nerves
- Begins at occipital bone and ends at vertebral disc between first and second lumbar vertebrae (bottom of ribs)
- Nerves for lower lumbar area and below, arise from end of spinal cord and make up the “cauda equina”
What are the functions of thr spinal cord?
- Provides a two way conduction pathway to and from the brain
- Conveys sensory impulses from the periphery to the brain, and conducts motor impulses from the brain to the periphery
- Provides a means of integrating reflexes **photo**
How does a reflex arc work?
1) Sensory receptor
2) Sensory neuron
3) Integrating centre
4) Motor neuron
5) Effrector
What is a reflex arc?
- Fast, automatic, unplanned sequence of actions in response to a stimulus
- A stereotyped response to a stimulus
- Important defense mechanism (Brain not involved immediately)
what is a somatic reflex?
If the effector is a skeletal muscle
what is an autonomic (visceral) reflex?
if the effector is a smooth muscle, cardiac muscle or gland
What are the 5 types of receptors?
1) mechanoreceptors
2) Chemoreceptors
3) Thermoreceptors
4) Photoreceptors
5) Nociceptors (pain receptors)
What are the functions of mechanoreceptors?
- detect stimuli related to touch, pressure, vibration, proprioception, hearing, equilibrium, and blood pressure
What are the functions of chemoreceptors?
- have the ability to sense chemicals, whether this is taste in the mouth, smell in the nose, or chemicals in body fluids
What is the function of thermoreceptors?
- Detects changes in tempurature
Function of photoreceptors
- detect light on the retina of the eye
Function of nociceptors
- detect pain, usually as a result of physical or chemical damage to tissues
What are cutaneous sensors?
sensory receptor found in the dermis or epidermis
What are proprioceptors?
a sensory receptor that responds to position and movement
What does olfactory receptors consist of?
1) Olfactory cells
2) Bipolar neurons with elongated axons and dendrites
3) Olfactory hairs on dendrite
4) Hairs extend into mucous
Olfactory receptor facts
- stimuli must be volatile as well as water and fat soluble
- Supporting cells
- Columnar epithelial cells of mucous membrane
What does olfactory mean?
- Nerve synapses with bulb. Tract ends up in olfactory area in temporal lobe of the cortex
What is the pathway of olfactory impulses from receptors to the cerebrum?
1) Axons of olfactory receptor cells unite in bundles to form olfactory nerves
2) Synapse with olfactory bulb neurons inside olfactory bulbs
3) Axons of olfactory bulb neurons unite to form olfactory tract, which goes to the olfactory cortex in temporal lobe
4) The only sensory information that does not go through thalamus
What is Hyposmia/
The reduced ability to smell
- Free nerve endings of olfactory cells in nasal mucosa are damaged over time
– About 1% of olfactory hairs lost per year
– Hyposmia affects 50% of those over 65, and 75% of those over 80.
– Can also result from injury, Alzheimer’s, Parkinson’s disease, drugs and smoking
Where are Gustatory receptors located?
located in taste buds on tongue, soft palate and pharynx
Where are taste buds located?
in elevated papillae.
- The taste buds, themselves, consist of many supporting cells surrounding 4 – 20 gustatory cells
Describe the sense of taste with respect to the structure of gustatory receptors
- Each gustatory cell has a single long microvillus projecting through a taste pore
- Sodium ions enter via sodium channels, causing depolarization (salty)
- Hydrogen ions enter via hydrogen channels, causing depolarization (sour)
- Chemicals that cause sweet, bitter and umami tastes fit into receptors, that then cause depolarization
- Taste impulses travel to medulla, then to thalamus, then to parietal lobe.
- The pattern of reception of the five different tastes create the sensation of many different tastes
- Taste buds are specialized for one taste, but are spread evenly over buccal surface
What are the besic taste sensations?
1) Sour
2) Sweet
3) Salty
4) Bitter
5) Umami
Autonomic nervous system facts / function
- Divided into sympathetic and parasympathetic divisions (AKA chart with father/son on dock)
- Many organs receive efferent neurons from both these divisions
- divisions are often antagonistic
- Hypothalamus – control centre
What is genrally different with sympathetic and parasymathetic divisions?
Neurotransmitters secreted by nerve ending
