Lecture 2 - CNS, PNS and Neurons Flashcards
What is neuroanatomy?
Structure and connectivity of the nervous system
What is neurophysiology?
how neurons work and communicate
Describe the components of the nervous system.
Made up of CNS and PNS
CNS - brain and spinal cord
PNS - autonomic and somatic
Autonomic further divided into sympathetic and parasympathetic
What is the function of the brain in the CNS?
Receives and processes information, initiates responses, stores memories, generates thoughts and emotions
What is the function of the spinal cord in the CNS?
Conducts signals to and from the brain, controls reflex activities
What is the role of the autonomic nervous system?
Controls Involuntary Responses
Consists of nerves responsible for:
- Regulates the automatic behaviors of the body (e.g., heart rate, blood pressure, respiration, digestion etc.)
Split into sympathetic - fight/flight
Parasympathetic - rest/digest
What is the role of the somatic nervous system?
Controls Voluntary Movements
Consists of nerves responsible for:
Transmitting signals from the CNS to the body for voluntary movement (efferent)
Delivering sensory information from the body to the CNS (afferent)
What is the hindbrain?
Consists of cerebellum medulla and pons
What is the function of the medulla?
- Part of brain stem
- Responsible for regulating:
Heart rate
Circulation
Respiration
Sleep/wakefulness
Level of arousal/consciousness
Reflexes (e.g., swallowing, coughing & sneezing, vomiting) - Origin point of cranial nerves IX-XII (responsible for sending and receiving motor and sensory information to and from pharynx, larynx, oesophagus, posterior third of the tongue, heart and digestive system)
What is the pons? And its function?
In hindbrain
Part of brain stem
‘Pons’ – means bridge in Latin
Contains various tracts linking the cerebral cortex to the cerebellum and the spinal cord
Responsible for regulating:
Arousal (brain attentiveness)
Sleep
Dreaming
Origin point of cranial nerves V-VIII (responsible for sending and receiving motor and sensory information to and from the head, face, eyes, inner ear, and anterior two thirds of the tongue)
What is the cerebellum? And its function?
In hindbrain
Not part of brain stem
Contains over 50% neurons in brain
Responsible for:
Fine motor coordination
Motor learning
Balance
Gait and posture
Proprioception
More recently considered to contribute to cognitive and affective processes
What is the midbrain? And its function?
Superior most part of the BRAINSTEM (medulla, pons, midbrain)
Origin point of cranial nerves III-IV (responsible for innervating eye muscles)
Separated into tectum posteriorly and tegmentum anteriorly
What is the tectum?
Superior Colliculus – orients towards visual stimuli
Inferior Colliculus – orients towards auditory stimuli
What is the tegmentum?
contains neurotransmitter nuclei involved in movement and arousal
What are the subcortical structures of the forebrain?
Limbic system, basal ganglia, hypothalamus, thalamus
What is the cerebral cortex?
Outermost layer of forebrain
Characterised by gyri and sulci. Responsible for our higher order cognitive functions as well as sending and receiving sensory and motor input and output.
Function of the frontal lobe
Movement, Executive Function, Working Memory, Judgement
Function of the parietal lobe
Somatosensory processing, attention, higher order visual processing
Function of the occipital lobe
visual processing
Function of the temporal lobe
Hearing, memory, higher or visual processing
What is the thalamus?
The relay station of the brain. Receives and filters input from the senses (excluding olfaction) and transmits to the cerebral cortex
What is the hypothalamus?
Regulates the endocrine system and the ANS. Controls body temperature, hunger, thirst and sexual behaviour.
What is the limbic system?
Made up of several structures including the thalamus and hypothalamus. Vital for motivation, emotion, learning and memory.
What is the basal ganglia?
Made up of several structures including the putamen and caudate. Vital for initiation and direction of voluntary movement.
What are the 12 cranial nerves?
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Spinal Accessory
- Hypoglossal
What are the key components of a neuron?
cell body
dendrites
axon
What are receptors?
specialized neural components responsive to specific types of energy (external stimuli)
Describe the structures of a neuron
Cell body (soma) - contains the nucleus of a neuron
Dendrite – tree branch-like structures extending from cell body, receiving electrical signal from terminal buttons of other neurons
Axon - Long thin structure that carries electrical impulse away from cell body towards terminal buttons
Terminal button – bud at the end of a branch of an axon – forms synapses with other neurons
Synapse – Junction between terminal button and membrane of another neuron
Neurotransmitter – chemical released by terminal buttons (can have excitatory or inhibitory effect on other neurons)
Glial cell - supporting cell that occurs in both the central and peripheral nervous system (e.g., oligodendrocytes, astrocytes and microglia)
Myelin Sheath – extension of a glial cell that wraps around the neuronal axon to provide insulation and facilitate electrical transmission
Nodes of Ranvier – a naked portion of a myelinated axon between adjacent glial cells helping to speed up electrical conduction
What are the consequences of myelin damage?
Damage to myelin coating affects neuronal function
Multiple sclerosis - an autoimmune disease affecting myelin and myelin producing glial cells in the CNS
Fatigue
Impaired motor function
Impaired sensory function (vision problems, tingling, pain)
Cognitive impairment
What is resting potential?
the difference in electric charge between the inside and outside of a neurons cell membrane (-70mv)
What is action potential?
electrical signal that is conducted along the length of the neuron’s axon to a synapse
What are the stages of action potential?
Depolarisation
Repolarisation
Hyperpolarisation (Refractory period)
Return to resting potential
Describe depolarisation
Electrical signal from receptor causes some Na+ channels to open and cell to depolarise
Once threshold potential (-55mv) is met, all Na+ channels open resulting in further depolarization
Describe repolaristation and hyperpolarisation
At peak depolarization (once Na+ reach equilibrium across the membrane) Na+ channels begin to close
K+ channels now open
K+ diffuses out of the cell causing the membrane potential become more negative (repolarise)
K+ continues to flow out of the cell causing the membrane potential to drop below that of the resting state (hyperpolarization)
Describe the return to resting state
Active process
Pumps three Na+ ions out and two K+ ions in
Returns membrane to resting potential
What are the properties of action potentials?
A propagated response along the axon
Remain the same size regardless of stimulus intensity
Upper firing rate is 500-800 impulses per second
Firing rate increases with increased stimulus intensity
Show spontaneous activity without stimulation
What happens during neurotransmission?
Neurotransmitters:
Relatively small molecules or peptides
Released by presynaptic neuron
Received by post-synaptic neuron
Matched with specific receptors
Facilitate change in membrane potential of post-synaptic neuron
What is an excitatory response?
response of a nerve fibre in which the firing response increases
e.g. glutamate
What is and inhibitory response?
response of a nerve fibre in which firing rate decreases
e.g. GABA
What is summation of the inhibitory and excitatory inputs?
If excitatory input stronger than inhibitory then neuron’s firing rate is high
If inhibition greater than excitation neuron’s firing rate is reduced
Firing rate is determined by shared inputs from excitatory and inhibitory neurotransmission
How does neurotransmission stop?
Reuptake – the neurotransmitter is transported back to the presynaptic cell to be recycled
Autoreception – autoreceptors in presynaptic cell inhibit further neurotransmitter release or synthesis
Enzyme degradation – a neurotransmitter is broken down by enzymes in the synaptic cleft
