CNS, PNS and Neurons Flashcards
How many neurons does it take to transmit pain from our foot to our brain?
3
How many neurons are needed to transmit a motor signal from our brain to our foot?
2
What does Neuroanatomy mean?
The structure and connectivity of the nervous system.
What does neurophysiology mean?
How neurons work and communicate.
what are the two divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS).
what re the two components of the CNS?
brain and spinal cord.
what is the function of the spinal cord?
to conducts signals to and from the brain, controls reflex activities.
What are the two subdivisions of the Peripheral nervous System?
Somatic and Autonomic.
What does the somatic nervous system do?
Controls voluntary movement.
What does the autonomic nervous system do?
Controls involuntary (automatic) responses.
What are the nerves in the Somatic Nervous System responsible for? (2)
- Transmitting signals from the CNS to the body for voluntary movement (efferent).
- Delivering sensory information from the body to the CNS (afferent).
What are the nerves in the Autonomic Nervous System responsible for?
- Regulating the automatic behaviours of the body – heart rate, blood pressure, respiration, digestion etc.
What are the two subsystems of the Autonomic Nervous System?
Sympathetic and Parasympathetic.
What does the Sympathetic Nervous System do?
stimulates (fight or flight response)
How does the Sympathetic Nervous System stimulate?
Accelerates heart rate, dilates pupils, decreases digestive functions.
What does the Parasympathetic Nervous System do?
Inhibits (rest and digest).
How does the Parasympathetic Nervous System inhibit?
Constricts pupils, decelerates heart rate, increases digestive function.
What are the main functions of the brain? (4).
Receives and processes information.
Initiates responses.
Stores memories.
Generates thoughts and emotions.
What are the 3 main sections of the brain?
Hindbrain.
Midbrain.
Forebrain.
What does the Hindbrain consist of?
Cerebellum, Pons and Medulla.
Where are the Pons and Medulla located?
In the Brain Stem.
What is the Medulla responsible for regulating? (6)
Heart rate,
Circulation,
Respiration,
Sleep / Wakefulness,
Levels of arousal / consciousness,
Reflexes (e.g. swallowing, coughing & sneezing, vomiting).
How does the Medulla achieve this regulation?
The medulla contains the origin points for a lot of nerve fibres, specifically cranial nerve fibres. These nerve fibres carry information from the brain stem to the structures in the head, face, neck and some organs.
What does Pons mean in Latin?
Bridge.
What is the Pons responsible for?
Regulating arousal, sleep and dreaming. Pons is also an origin point for a lot of nerve fibres.
Where is the Cerebellum?
The Cerebellum sits at the base of the brain behind the brainstem.
What does cerebellum mean in Latin?
Little brain.
What is important about the structure of the Cerebellum?
The cerebellum has a similar structure to the brain however, the folds are much tighter which allows the cerebellum to contain over 50% of the neuron’s in the brain despite only accounting for less than 10% of its weight.
What is the Cerebellum responsible for?
Fine motor coordination, motor learning, balance, gait & posture and proprioception.
What is Proprioception?
Our sensation of our body and limbs in space.
Where is the Midbrain?
The midbrain also makes up part of the brainstem.
What does the Midbrain consist of? (2)
Tectum and Tegmentum.
What are the two sections within the Tectum?
Superior Colliculus and Inferior Colliculus.
What does the Superior Colliculus do?
Orients us towards visual stimuli.
What does the Inferior Colliculus do?
Orients us towards auditory stimuli.
What is in the Tegmentum?
The Tegmentum contains neurotransmitter nuclei involved in movement and arousal.
Why is the Substantia Nigra black?
The Substantia Nigra contains a very high concentration of Dopaminergic Neurons, one of the by-products of dopamine is near-melanin which causes the surrounding tissue to become stained in the this black colour.
What are Dopaminergic Neurons?
Neurons that produce Dopamine.
Why is Dopamine so important?
Dopamine is an essential neurotransmitter for motor initiation.
What causes Parkinson’s Disease?
The death of Dopaminergic Neurons in the Substantia Nigra. Therefore, the dark pigmentation is lost as the cells of the Substantia Nigra start to die, the death of these neutrons causes other parts of the brain to become dysfunctional causing the common traits of Parkinson’s.
Why do we require the forebrain?
We could live with just the Hindbrain and Midbrain but we require the Forebrain to make us human.
What does the Forebrain consist of? (4)
Limbic System.
Basal Ganglia.
Hypothalamus.
Thalamus.
What is the Cerebral Cortex?
The overarching name for the components of the Forebrain, cortex just means outer layer therefore, the cerebral cortex is just the outer layer of the cerebrum.
What is important about the structure of the Cerebral Cortex?
The cerebral cortex has a lot of folds which allows it to have a large surface area.
What are the Gyri?
The Gyri are the ridges in the brain.
What are the Sulci?
The Sulci are the grooves in the brain.
Why are the Hindbrain and Midbrain hidden?
In humans, the forebrain is so large it hides the hindbrain and midbrain. Mammals have the largest forebrains.
What is the Frontal Lobe responsible for?
Movement.
Executive Function.
What is involved in executive function? (5)
Planning.
Problem Solving.
Abstract Thinking.
Working Memory.
Judgement.
An example of Forebrain controlling personality:
Finneas Guage, got a rod straight through his frontal lobe and it changed his personality entirely.
What is contained in the precentral gyrus?
Primary Motor Cortex.
What is the Parietal Lobe responsible for?
Somatosensory Processing.
Attention.
Higher Order Visual Processing.
What does Somatosensory mean?
Refers to any senses that aren’t from our primary sense organs e.g. sensations from body, skin, muscles etc. rather than from eyes, ears, mouth, nose etc.
What does the Parietal Lobe also do?
Directs attention which is also linked to vision, therefore refers to understanding where things are in space.
What is the Occipital Lobe?
The visual processing cortex.
What is the Temporal Lobe responsible for?
Hearing.
Memory.
Higher Order Visual Processing.
What does the Temporal Lobe allow us to do?
Allows us to remember and recondite people and certain things.
What are the Primary Sensory Areas?
Each of the areas of the cerebral cortex have different regions that are responsible for processing specific types of sensory information. These are known as the Primary Sensory Areas.
What does the Spinal Cord do?
Conducts signals to and from the brain and controls reflex activities.
What are Reflex Activities?
What does Homunculus mean?
The complexity of a function determines how much of our cortex will be devoted to a particular body region, not the size of the body part.
What are the Subcortical Structures of the forebrain?
Thalamus.
Hypothalamus.
Basal Ganglia.
Limbic System.
What is the Thalamus and what does it do?
The relay station of the brain, it receives and filters input from the senses (excluding olfaction) and transmits to the cerebral cortex.
What does the Hypothalamus do?
Regulates the endocrine system and the autonomic nervous system. Controls body temperature, hunger, thirst and sexual behaviour.
What are the four F’s?
What is the Limbic System and what does it do?
The limbic system is made up of several structures including the thalamus and hypothalamus. It is vital for motivation, emotion, learning and memory.
What is the Basal Ganglia and what does it do?
Made up of several structures including the putamen and caudate. Vital for initiation and direction of voluntary movement.
What are the three key components of a neuron?
Cell Body, Dendrites and Axon / Nerve Fibres.
What are receptors?
Specialised neural components responsive to specific types of energy (external stimuli).
What does the Cell Body (stoma) contain?
The nucleus of the neuron.
What is the structure of dendrites?
Tree-branch-like structures extending from the cell body, receiving electrical signals from terminal buttons of other neurons.
What is the structure of axons?
Long, thin structure that carries electrical impulse away from the cell body towards the terminal buttons.
What are the Terminal Buttons and what are their function?
Buds at the end of a branch of an axon, form a synapse with other neutrons.
What is a Synapse?
The junction between the terminal button of one neuron and the membrane of another.
What is neurotransmitter?
The chemical released by terminal buttons, can have excitatory or inhibitory effects on other neurons.
What are Glial Cells?
Supporting Cells that occur in both the central and peripheral nervous system.
Name 3 examples of Glial Cells.
Oligodendrocytes, astrocytes and microglia.
What is the Myelin Sheath and what is its function?
An extension of a glial cell that wraps around the neuronal axon to provide insulation and facilitate electrical transmission.
What are the Nodes of Ranvier?
A naked potion of a myelinated axon between adjacent glial cells, helping to speed up electrical conduction.
What are the three types of Neurons?
Sensory, Inter and Motor.
What is Multiple Sclerosis and what causes it?
Multiple Sclerosis is an autoimmune disease affecting myelin and myelin producing glial cells. Damage to myelin coating affects neuronal function.
What are the common traits of MS?
Fatigue.
Impaired Motor Function.
Impaired Sensory Function (visual problems, tingling, pain).
Cognitive impairment.
What is an Action Potential?
The rapid increase in positive charge of a neuron that travels down the axon - also called a ‘nerve impulse’.
What are the 4 stages if an Action Potential?
Depolarisation.
Depolarisation.
Hyperpolarisation.
Return to resting potential.
What does Depolarisation mean?
An electrical signal from a receptor causes some Na+ channels to open and the cell to depolarise.
What is the threshold potential?
-55mv
What happens once the threshold potential is met?
All Na+ channels open resulting in further depolarisation.
What is peak depolarisation?
Once Na+ reaches an equilibrium across the membrane. ~40mv.
What happens at peak depolarisation?
Na+ channels begin to close.
What is repolarisation?
Once Na+ channels have closed, K+ channels open meaning that K+ diffuses out of the cell causing the membrane potential to become more negative.
What is hyper-polarisation?
K+ continues to flow out of the cell causing the membrane potential to drop below that of the resting state.
What doe the ‘return to resting potential’ stage involve?
It is an active stage is which 3 Na+ ions are pumped out for every 2 K+ ions pumped in. This returns the membrane to resting potential, meaning it is ready to produce another action potential.
What does resting potential mean?
The difference in charge between the extracellular and intracellular space when nerve fibre is not conducting electrical signals.
What is resting potential (number) and what does this mean?
-70mv, meaning the inside of the fibre is negative relative to. he outside.
Describe Neurotransmitters. (5)
Neurotransmitters are relatively small molecules or peptides which are released by the presynaptic neuron and received but he post-synaptic neuron. Neurotransmitters are matched with specific receptors and they facilitate change in the membrane potential of the post-synaptic neuron.
How do neurotransmitters initiate an action potential?
Neurotransmitters can be excitatory or inhibitory.
Give an example of an excitatory neurotransmitters.
Glutamate.
Give an example of an inhibitory neurotransmitter.
GABA.
What does GABA stand for?
Gamma-Aminobutyric Acid
Give an example for two neurotransmitters that can both excitatory and inhibitory and explain why.
Dopamine and Acetylcholine - it depends on the binding receptor.
How is firing input determined?
The shared inputs from excitatory and inhibitory neurotransmission; if inhibition is greater than excitation the neuron’s firing rate is reduced whereas if excitation is greater the inhibition neuron’s firing rate is high.
What are the 3 ways Neurotransmission stops?
Reuptake, Autoreception and Enzyme Degradation.
What happens during reuptake?
The neurotransmitter is transported back to the presynaptic cell to be recycled.
What happens during autoreception?
Autoreceptors in the presynaptic cell inhibit further neurotransmitter release or synthesis.
What happens during enzyme degradation?
A neurotransmitter is broken down by enzymes in the synaptic cleft.
match these six terms into two groups of three:
afferent, efferent, brain -> PNS, receptors -> CNS, outside spinal cord, in the ventral horn of the spinal cord.
afferent, receptors -> CNS, outside the spinal cord.
efferent, brain -> PNS, in the ventral horn of the spinal cord.
