Nervous system Flashcards
What is the central nervous system (CNS)
It consists of the brain and spinal cord, and is responsible for receiving, processing and responding to sensory information
What is the peripheral nervous system
It consists of the cranial nerves, the spinal nerves, and its function is to transmit sensory information from peripheral receptors to the CNS
It controls motor pathways
What is the automatic nervous system
It is a part of the PNS, and regulates involuntary physiological processes such as heart rate, blood pressure, digestion and respiratory rate. Operates automatically without conscious effort
What are the subsections of the PNS?
Motor pathways and sensory pathways
What are the subsections of motor pathyways?
The automatic nervous systsem and the somatic nervous system
What is the somatic nervous system
Your somatic nervous system is a subdivision of your peripheral nervous system, which is all of your nervous system except your brain and spinal cord.
Your somatic nervous system allows you to move and control muscles throughout your body. It also feeds information from four of your senses — smell, sound, taste and touch — into your brain.
What are the subsections of the ANS?
sympathetic and parasympathetic divisions
What is the sympathetic division
The sympathetic system controls “fight-or-flight” responses. In other words, this system prepares the body for strenuous physical activity. The events that we would expect to occur within the body to allow this to happen do, in fact, occur.
This can include control of your heart rate, blood pressure, digestion, urination and sweating, among other functions.
What is the parasympathetic division
The parasympathetic system regulates “rest and digest” functions.
Digestion, urination, salivation, excretion etc.
What is the sensory pathway
This transmits the various senses received by receptors into the PNS
What are the two components essential to the function of the CNS
Afferent and efferent pathways
What is the afferent pathway
It is the sensory division of the PNS
Afferent neurons carry information from sensory receptors of the skin and other organs to the central nervous system (i.e., brain and spinal cord)
What is the efferent pathway
It is the motor division of the PNS
efferent neurons carry motor information away from the central nervous system to the muscles and glands of the body.
What is the forebrain? WHat does it include?
The largest region of the brain. It contains the cerebral cortex, thalamus, hypothalamus, pineal gland and limbic system with it
The forebrain is responsible for voluntary actions, thinking, and processing. The forebrain interprets sensory input and makes decisions.
What is the hindbrain? WHat does it include?
The hindbrain contains several structures that regulate autonomic functions, which are essential to survival and not under our conscious control.
Includes the brainstem and cerebellum.
What does the brainstem include?
Midbrain, pons and medulla
What does the midbrain do
Connects rest of the brainstem to cerebral cortex
What does the pons do
It is the “bridge” between midbrain and medulla
What does the medulla do
It is where the brain transitions into the spinal cord
What does the spinal cord do
The three primary roles of the spinal cord are to send motor commands from the brain to the body, send sensory information from the body to the brain, and coordinate reflexes.
What is the cerebral cortex and explain its structure
The cerebral cortex is the outer layer of your brain’s surface, located on top of the cerebrum. The cerebral cortex carries out essential functions of your brain, like memory, thinking, learning, reasoning, problem-solving, emotions, consciousness, and sensory functions.
It is divided into right and left cerebral hemispheres. It is connected by the corpus callosum (the bridge). Each hemisphere is divided into lobes; frontal, parietal, temporal and occipital
What are the four lobes of the cortex
The frontal lobe, parietal lobe, temporal lobe and occipital lobe
What is the function of the frontal lobe
It is where higher executive functions including emotional regulation, planning, reasoning and problem solving occur
What is the function of the parietal lobe
It integrates sensory information, including touch, temperature, pressure and pain
What is the function of the temporal lobe
It processes sensory information, important for hearing, recognising language and forming memories
What is the function of the occipital lobe
Major visual processing center in the brain
What is the function of the thalamus
It processes sensory information
Your thalamus is your body’s information relay station. All information from your body’s senses (except smell) must be processed through your thalamus before being sent to your brain’s cerebral cortex for interpretation.
What is the function of the hypothalamus
Major control center for the automatic motor system. Involved in some hormonal activity and connects hormonal and nervous system. Helps regulate homeostasis
What is the function of the pineal gland?
Produces hormone melatonin, which regulates sleep-wake cycles
What is the function of the limbic system
It regulates behavioural and emotional responses. Most important parts are the hippocampus and amygdala
What is the function of the basal ganglia
It is used to control voluntary motor movements, habit learning, eye movement, cognition and emotion
What is the function of the cerebellum
Coordinates gait and maintains posture. It also controls muscle tone and voluntary muscle activating, but is unable to initiate muscle contraction
It receives information about:
Voluntary muscle movements from cerebral cortex and from muscles, tendons and joints. And also balance
What is the function of the brainstem
Connect forebrain to spinal cord and cerebellum.
Responsible for vital functions of life; breathing, consciousness, blood pressure, heart rate and sleep
CNS pathway
Function of the spinal cord? Explain the segments of the spinal cord
Carries motor and sensory signals between brain and periphery and coordinates reflexes
Organised into segments, with each segment having a pair of spinal nerves (efferent and afferent information)
There are 4 components to the spinal cord
Also, the gray matter is inside the spinal cord, whereas the white matter is on the outside of the spinal cord
What are the 4 components of the spinal cord
Cervical spine(8), thoracic spine(12), lumbar spine (5), sacral spine (5)
The sacral region (sacrum) is at the bottom of the spine and lies between the fifth segment of the lumbar spine (L5) and the coccyx (tailbone). The sacrum is a triangular-shaped bone and consists of five segments (S1-S5) that are fused together.
What does decussation mean
The crossing of the right and left corticospinal tract
Explain decussation in the spinal cord
Sensory pathways decussate (cross over) from one side of the CNS to the other. As such, each cerebral hemisphere receives sensory information from opposite side of the body
Motor pathways decussate from one side of CNS to the other
WHat are the peripheral nerves
Peripheral nerves reside outside your brain and spinal cord. They relay information between your brain and the rest of your body.
What are cranial nerves
The cranial nerves are a set of 12 paired nerves in the back of your brain. Cranial nerves send electrical signals between your brain, face, neck and torso. Your cranial nerves help you taste, smell, hear and feel sensations. They also help you make facial expressions, blink your eyes and move your tongue.
they are more complicated
What are dermatomes
Dermatomes are areas of skin that connect to a specific nerve root on your spine.
What does the ANS control?
Cardiac muscle
Smooth muscle
Exercise glands
Endocrine glands
What is the neurone/neuron
It is the basic structural unit of nervous system (it is a nerve cell)
Each neurone is an individual cell which communicates at synapses
It is a single body with dendrites and axons
What are synapses
The places where neurons connect and communicate with each other are called synapses.
What are the main components of neurons?
Dendrites, nucleus, node of Ranvier, myelin sheaths, shwann cell, axon, axon terminals
What do dendrites do?
The main function of dendrites is to receive information from other neurons, called pre-synaptic neurons, or from the environment
What does the node of Ranvier do?
Nodes of Ranvier are gaps in the myelin sheath coating on the neural axon. The myelin allows the electrical impulse to move quickly down the axon. The nodes of Ranvier allow for ions to diffuse in and out of the neuron, propagating the electrical signal down the axon.
Allows for the jumps
What does the myelin sheath do
Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells.
WHat does the axon do
From the broadest perspective, the function of axons is to carry electrical impulses that are the means of communication within the brain and between the brain and the rest of the body.
What does the axon terminal do
An axon terminal contains many vesicles filled with neurotransmitters which allows the neuron to conduct electrical impulse down to another neuron or another type of cell by the release of signals into the synapse.
What is depolarisation
Less negative charge inside cell compared to outside
What is repolarisation
More negative charge inside cell compared to outside, which occurs right after depolarisation
Explain the resting potential of the neuron?
It has a resting potential of -70mV. This is because of the Na and K ions.
This is because K+ concentration is higher inside the cell than outside, and Na+ is higher outside the cell than inside. Ultimately, there is a lower charge inside the neuron compared to outside of the neuron leading to a negative resting potential.
What is the role of the voltage gated ion channels in the neuron
They are there to respond to a depolarisation of the cell membrane, which would cause it to open up and allow Na+ to come into the cell, further causing depolarisation in the cell. However, once it reaches a certain
Explain the process of the action potential
The resting membrane potential of the neuron is at -70mV. When the dendrites receive a signal from the synaptic cleft, and the cell body decides that it is a significant enough signal (meeting the threshold potential), it leads to the staggered depolarisation of the neuron. This depolarisation is caused by the open voltage gated ion channels which allow for the influx of Na+ ions into the neuron. However, once it reaches a certain point, the voltage gated ion channels close. However, the change in membrane potential also opens the potassium voltage gated channels, causing potassium to leave the cell via diffusion. As such, this causes repolarisation. This repolarisation typically overshoots causing a hyperpolarisation, where the cell membrane potential drops below the resting potential, and eventually comes back up to equilibrium via the Na-K pump
This repolarisation process is important as it allows for the signal to be transmitted down the axon without the signal being transmitted back up as it is still undergoing repolarisation and needs a higher than normal stimulus to bring it back
What is the threshold potential
Minimum resting membrane potential for a signal to be transmitted. Anything below won’t work (~-55mV)
What is the function of myelin
The myelin increases speed of nerve conduction. It is present around nerves in the CNS and PNS and insulates axons. It is made up of about 80% lipid
Here, action potentials can’t be generated while myelin is wrapped around it –> prevents creation of an action potential
What are the node of ranviers?
These are points on the axon which has no myelination present
What is saltatory conduction
Describes how an electrical impulse skips from node to node down the length of an axon. In myelinated axons, action potentials generated at the nodes –> saltatory conduction. This increases speed of action potential propagation compared to continuous conduction across unmyelinated axons, as they cause the action potentials to move more rapidly by ‘jumping’ –> speeds up transmission on axon
What is the synapse
Place where neurons connect and communicate to each other
What happens at an axon terminal?
when an action potential reaches the axon terminal, Ca2+ moves in, allowing neurotransmitter release. Neurotransmitters diffuse across synaptic cleft to bind with receptors on the post synaptic neuron.
What happens to neurotransmitters
They are broken down by enzymes or undergo reputake into the presynaptic neurone
What is the synpatic cleft
The synaptic cleft—also called synaptic gap—is a gap between the pre- and postsynaptic cells that is about 20 nm (0.02 μ) wide. The small volume of the cleft allows neurotransmitter concentration to be raised and lowered rapidly.
What is the role of receptors in synaptic function
They are on the postsynaptic neuron and allow for the neurotransmitters to bind onto them which allows for further propagation of the action potential
What is a excitatory post synaptic potential?
An excitatory postsynaptic potential (EPSP) occurs when sodium channels open in response to a stimulus. The electrochemical gradient drives sodium to rush into the cell. When sodium brings its positive charge into the cell, the cell’s membrane potential becomes more positive, or depolarizes.
What is a inhibitory post synaptic potential?
An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential.
What is a common neurotransmitter which promotes excitatory post synaptic potential?
glutamate
What is a common neurotransmitter which promotes inhibitory post synaptic potential?
GABA
How does glutamate promote excitatory post synaptic potential?
Glutamate acts as a major excitatory neurotransmitter. It opens Na+ channels in post synaptic membranes, causing excitatory post synaptic potentials, and a depolarisation. Ultimately it increases the chances of a neuron undergoing the action potential.
How does GABA promote inhibitory post synaptic potential
It acts as a major inhibitory neurotransmitter. It works like this through opening Cl- channels in post synaptic membrane. This causes further hyperpolarisation, reducing the chances of the neuron being stimulated to the threshold potential, thus inhibiting the signals.
Basically by opening Cl- channels, Cl- is greater in extracellular fluid compared to intracellular, and Cl- will enter the cells –> more -ve –> decreased chances of action potential occurring
What is temporal summation
Big stimulus from a single presynaptic terminal into a single axon –> lots of action potential –> release of glutamate into cleft –> multiple EPSPs which increase resting potential
What is spatial summation
Multiple synaptic inputs into multiple dendrites. Each dendrite wont have enough EPSPs on its own to trigger action potential, but together it can increase resting membrane potential to threshold potential
