WEEK FIVE - SYNAPSES AND NEURAL INTEGRATION, BRAIN STRUCTURE AND FUNCTION, BRAIN FUNCTION AND CRANIAL NERVES Flashcards
Describe where on a neuron a synapse may occur
Between axons, soma or dendrites
First neuron releases neurotransmitter onto second neuron that responds
1st neuron = pre-synaptic
2nd neuron = post-synaptic
Describe how neurotransmitters are categorised by their chemical structure and give examples of the major neurotransmitter classes
- Amino acid neurotransmitters
Excitatory amino acids
[glutamate: MOST COMMON excitatory neurotransmitter in CNS]
Inhibitory amino acids
[GABA (gamma amino butyric acid): MOST COMMON inhibitory neurotransmitter in CNS]
- Acetylcholine [acetic acid + choline]
- Monoamines [modified amino acids]
Catecholamines
- adrenaline [epinephrine], noradrenaline [norepinephrine] and dopamine
Indolamines
- serotonin and histamine
- Neuropeptides
- neuropeptides, endorphin, dynorphin
Still being discovered every few years
Explain what determines whether a neuron will fire an action potential in response to synaptic input
Binding of neurotransmitter to postsynaptic membrane = voltage change in membrane potential
POSITIVE voltage from excitatory neurotransmitters = post-synaptic cell to be MORE likely to fire
Result from Na+ flowing into cell
~30 EPSPs [excitatory postsynaptic potentials] needed to reach threshold
Enough EPSPs arriving quickly = action potential
Explain how pre-synaptic inhibition may reduce the ability of a neuron to release neurotransmitter
One presynaptic neuron suppresses another
Neuron release inhibitory neurotransmitter onto presynaptic neuron(s) eg GABA
Prevents voltage-gated calcium channels from opening - releases less or no
Explain how the nervous system translates complex information into a simple code
All information that is sent –> CNS + everything within CNS = sent as ACTION POTENTIALS
Qualitative information [eg taste/hearing] depends upon which neuron fire
Labelled line code: brain knows what type of sensory information travels on each nerve fibre
Quantitative Information
Weak stimuli excites only specific neurons
WEAK signal = SLOWER frequency of APs
Stronger stimuli excite these ^ ++++ other neurons with high thresholds
Strong signal = HIGH frequency of APs
Stronger stimuli = more rapid firing rate
CNS judges stimulus strength from firing frequency of sensory neurons
State and identify the major subdivisions and anatomical landmarks of the brain
cerebrum -83% of brain vol. [split in hemispheres]
cerebellum - 50% of neurons - CAUDAL
diencephalon [hypothalamus, thalamus and epithalamus] -CAUDAL
midbrain
hindbrain [cerebellum, pons, medulla oblongata]
brainstem [diencephalon, midbrain, pons, medulla oblongata
Describe and identify the meninges of the brain
DAP acronym
dura mater [outer]
Outer periosteal layer against bone
Inner meningeal layer
two layers are separated in parts to form dural sinuses [drains blood from brain]
arachnoid mater [middle]
extensions - arachnoid villi [granulation] that pierce dura and extend into sinuses
pia mater [inner]
subarachnoid space between pia - arachnoid mater = blood vessels and flow of CSF
Describe and identify the ventricles within the brain
Lateral ventricles in cerebral hemispheres
Third ventricle = single vertical space under corpus callosum
Cerebral aqueduct runs through midbrain
Fourth ventricle = chamber between pons and cerebellum
Central canal runs down through spinal cord
Describe the production, circulation and function of cerebrospinal fluid (CSF)
- Produced within ventricles by choroid plexus [blood capillaries in each Lateral ventricle] TOP
Circulation
- flows into third ventricle [adds more CSF]
- flows down cerebral aqueduct to fourth ventricle
[adds more CSF]
- fills subarachnoid space of brain/spinal cord
- at arachnoid villi - CSF reabsorbed into sinuses
Function
-Gives buoyancy to brain and spinal cord
-Protection from blows and other trauma
-Nourishes brain - contains nutrients + hormones
Explain the significance of the blood brain barrier (BBB) system
Maintain the homeostasis of the brain microenvironment
shields the brain from toxic substances in the blood, supplies brain tissues with nutrients, and filters harmful compounds from the brain back to the bloodstream.
BBB allows lipid soluble materials into brain
eg water, oxygen, carbon dioxide, and general anesthetics
List the components of the hindbrain and midbrain and describe their functions
Cerebellum [LARGEST part of hindbrain]
controls
- muscle coordination and motor learning, posture,
balance and muscle tone
midbrain - nuclei of cranial nerves 3+4
Short segment of brainstem between diencephalon superiorly and pons inferiorly
controls visual and auditory reflexes + levels of arousal/ consciousness
Pons - nuclei of cranial nerves - 5, 6, 7, 8
controls
- Posture, sleep, hearing, balance, taste, eye
movements, facial expression, facial sensations,
respiration and swallowing
Medulla Oblongata - Nuclei of cranial nerves - 9,10,11,12
controls
- Rate and force of heartbeat
Blood vessel diameter
Rate and depth of breathing
Coughing, sneezing, gagging, swallowing, vomiting,
salivation, sweating, movement of tongue and
head
List the 3 major components of the diencephalon & their location & describe their function
Thalamus - most superior part of diencephalon
between midbrain and cerebrum
immediately caudal to corpus callosum
Receives ALL sensory information [except smell] on its way to cerebral cortex
also involved in movement coordination
Hypothalamus - Inferior to thalamus
Superior to pituitary gland
controls - centre for homeostasis
- Thermoregulation
- Food and water intake
- Sleep/circadian rhythms
- Emotional behaviour
- controls ANS
Epithalamus - composed mainly of pineal gland
controls
- circadian rhythms
- Synthesises melatonin [promotes sleepiness]
Identify the 5 lobes of the cerebrum and state their functions
FRONTAL LOBE
Voluntary motor functions
Planning, mood, smell and social judgement
PARIETAL LOBE
Receives and integrates sensory information
OCCIPITAL LOBE
Visual centre of brain
TEMPORAL LOBE
Area for hearing [primary auditory cortex], smell, language, memory and emotional behaviour
INSULA [small mass of cortex deep to lateral sulcus]
Gustation and visceral sensations
List & describe the 3 types of tracts in the cerebral white matter
Projection tracts
From brain → spinal cord
Commissural tracts
Cross to opposite hemisphere via corpus callosum [mid-sagittal area between hemispheres]
Anterior and posterior commissures
Association tracts
Connect lobes and gyri within hemisphere
Describe location & function of basal nuclei & the limbic system
Masses of grey matter within cerebrum located deep to cortex and lateral to thalamus
- voluntary control of skeletal muscle particular starting and stopping of movement
Limbic system [associated with emotion]
Facilitates memory storage and retrieval
Behavioural and emotional responses - particular survival
Contains:
- Amygdala [involved with fearful/anxious emotions]
- Hippocampus [interconnected with amygdala
associated more with memory than emotion]
- Thalamus
- Cingulate gyrus [superior to corpus callosum, involved with aspects of emotion/memory]
