Brain Structure and Function Flashcards
What is the brain made of?
Neurons (functional units)
Glial cells (underdogs; 1 billion supporting cells):
- Astrocytes
- Microglia
- Oligodendrocytes
- Meninges
- Subarachnoid space
What are neurons? What types are there?
Functional units of the brain (nerve cells); CNS contains > 10^11.
- Sensory; from periphery to CNS (afferent info e.g. pin prick)
- Motor; from CNS to periphery (e.g. brain to muscle)
- Interneurons; sensory to motor (relay neurons; connect)
What are glial cells, and how do they differ from neurons?
- Supporting cells of the brain
- Don’t have axons or dendrites
What are astrocytes?
- ‘Star-like’ glial cells
- Outnumber neurons by fivefold
- Have many processes e.g. maintain BBB
What is the function of microglia?
- Type of glial cell
- Have an immune function (phagocytic; mopping up debris, dead neurons)
What is the function of oligodendrocytes?
- Type of glial cell
- Provide structural support (hold neurons in place)
What is the function of meninges? What layers form it?
- Type of glial cell
- Protects the brain from ‘damage’
- 3 layers; PAD
P; Pia mater (v.soft and delicate, direct contact w/brain)
A; Arachnoid membrane (spider-web like appearance)
D; Dura mater (tough, direct contact with bone)
What does the acronym ‘PAD’ refer to?
The three layers of the meninges:
Pia mater
Arachnoid membrane
Dura mater
How many ventricles does the brain have? What is their function?
Four ventricles; the lateral ventricles (right and left in the cerebrum), the third ventricle (tucked under and central of the lateral) and the fourth ventricle (at the upper half of the medulla oblongata at the back)
- The ventricles are filled with CSF (cerebrospinal fluid), made by ependymal cells of the choroid plexus (found in each one)
- CSF protects the brain (further to the meninges), and provides buoyancy, suspending the brain (so it does not rest on the floor of the cranium, destroying neurons)
- CSF circulates through the ventricles and the subarachnoid space (between the pia mater and the arachnoid membrane)
What are the main milestones during prenatal brain development?
- When the neural tube (embryonic tissue) starts folding, this is development (from 25 days)
- Brain development is taking shape at 5 months (beginning from 2 weeks)
- Full development at 9 months
What birth defects may occur as a result of improper neural tube folding?
Various birth defects of the brain and spinal cord:
- Spina bifida; spinal column has not folded properly e.g. meninges, resolved by surgery only
- Anencephaly; incomplete brain/skull development, or facial defects too (most neonates will not survive)
What are neurons and glial cells (e.g. oligodendrocytes/astrocytes) formed from?
- Stem cells (undifferentiated); derived from ectoderm, embryonic tissue that is precursor for the CNS
- These become progenitor cells ‘direct ancestor’ stem cells that has instruction of what to differentiate into
- Then these become lineage restricted progenitor cells, undergoing differentiation into:
Neurons, oligodendrocytes or astrocytes etc.
Where is the brainstem? What parts is it made up of?
- Connects spinal cord to rest of brain
- 3 regions: medulla oblongata (ventral = bottom), pons (middle), midbrain (dorsal = top)
What is the medulla’s (of the brainstem) function?
- Centre for respiration and circulation (important)
- Dorsal region of brainstem
What is the function of the pons (of the brainstem)?
- Bridge between different brain regions
- Assists in controlling autonomic function; sleep and arousal, as well as respiration, and REM sleep
What is the function of the midbrain? What is a common indication that arises from its dysfunction/death?
- Controls body movement
- Location for substantia nigra; where dopaminergic neurons originate
- Hence death of neurons here = Parkinsons symptoms
- Also relays auditory and visual information
What is the role of the cerebellum? Where is it located?
- Little brain (Latin)
- Coordinates fine muscle movement and balance (e.g. writing too)
- Impairment results in ataxia (lack of coordination, speech affected too)
- At bottom of skull, behind the brainstem
Where is the hypothalamus located, and what is its function?
- Lies above brain stem
- Regulates body temperature (thermoregulatory centre, feeding, sexual behaviour, sleep - homeostasis
- Gives rise to the pituitary gland; responsible for release of hormones such as vasopressin/ADH
Where is the thalamus located, and what is its function?
- Above and centre of the hypothalamus
- Acts as the brain’s sensory switchboard
- Relays information to and from the cortical regions (higher centre)
What is the function of the corpus callosum?
- Connects left and right hemispheres of the brain
- Agenesis seen with incomplete development of the corpus callosum; seizures/cognitive functions impaired, due to impaired flow of information
What is the cerebral cortex, and what forms it?
- Largest and most highly developed region of the brain (big outer ‘brainy’ bit)
- Divided into multiple lobes:
> Frontal lobe (front bit)
> Parietal lobe (mid-high bit)
> Occipital lobe (back)
> Temporal lobe (lower-middle bit)
What is the frontal lobe (cerebral cortex) responsible for? What regions are there?
Two parts:
- Prefrontal cortex; intellectual function, executive decision-making e.g. emotional behaviour (suppresses aggressive behaviour)
- Motor cortex; contains the premotor and primary motor cortex, responsible for movement.
What is the parietal lobe (cerebral cortex) responsible for?
- Processes sensory information associated with taste, temperature, touch
- Knowledge of numbers, orientation (proprioceptors detect where you are in space) etc.
What is the occipital lobe responsible for?
- Occipital = ocular
- Entirely for processing visual information (optic nerve etc)
- Hence ‘seeing stars’ if bang back of head
What is the temporal lobe responsible for?
- Primary auditory cortex (hearing)
- Some visual cognition due to close association/proximity w/occipital lobe
What is the purpose of the basal ganglia? Where is it located?
- Multiple subcortical nuclei at base of forebrain
- Associated with the cerebral cortex
- Associated w/motor coordination; initiates and coordinates activities such as walking
- Inhibits/filters out unwanted or unnecessary movements
How is the basal ganglia related to Parkinson’s disease?
- Movement control disrupted due to death of basal ganglia neurones in Parkinson’s
- Unable to filter out unnecessary movements
What are the three main regions of the basal ganglia?
- Putamen
- Caudate nucleus
- Globus pallidus
What is the limbic system? What regions form it?
'The emotional brain' - Central/middle bit > Hippocampus > Cingulate gyrus > Amygdala > Hypothalamus and thalamus
What is the hippocampus responsible for? What system does it belong to?
- Long term memory (primary role)
- Inhibition of behaviour (e.g. disciplined child won’t do a certain thing again)
- Spatial navigation (black cab drivers have enlarged hippocampus)
- Alzheimer’s disease (memory)
> Part of the Limbic system
What is the function of the cingulate gyrus? What system does it belong to?
- Coordinates sensory input with emotions
- Connected to the hippocampus and the hypothalamus; makes sure input is coordinated accordingly
> Part of the Limbic system
What is the function of the amygdala?
Most influential region of limbic system WRT emotion:
- Anger
- Anxiety
- Fear
(Also aggression, memory, sadness, sex drive, binge drinking)
How do the hypothalamus and thalamus relate to the Limbic system?
They both are associated with emotional behaviour (as well as homeostatic mechanisms for the hypothalamus, and the sensory switchboard role of the thalamus)
Where is the motor homunculus and what is it responsible for?
- Left middle outer strip of brain
- Fine movement; lot of brain matter involved, e.g. fingers
- Lips, chewing/salivation/vocalisation, face, body movement etc
Where is the sensory homunculus and what is it responsible for?
- Right middle outer strip of brain
- Fingers/mouth/lips have a lot of brain matter dedicated to sensing shit
