Brain Bee 2024

What is the ratio between glial cells and neurons?

1:1

How many specialised glial cells are there?

5

what are the 5 functions of astrocytes?

1. deliver nutrients

2. control chemical environment

3. control capillary flow - chemicals in blood

4. repair and play a role in scarring of nerve cells in the CNS following injury

5. provide a buffer reserve of fuel for cells

what are the 4 functions of microglia?

1. scavenge cell debris from dying neurons

2. first responders to damage to CNS

3. constantly and rapidly reorganize their shape - effectively scan local environment

4. role in development of brain after birth + brain plasticity

what do ependymal cells have and what does this mean

cilia - hair like cells that influence distribution of neurotransmitters and direct CSF by timing their movements within the cavity of ventricles

how can ependymal cells lead to neuroregeneration

can divide and form neurons throughout their life

how can ependymal cells replenish neurons

protect axon stumps from degeneration after damage and allow alternate neuronal connections to grow and restore function to replenish a portion of dead neurons

tropic hormones

work on other endocrine glands

trophic hormones

hormones of the anterior pituitary gland that aid in growth, development of other molecules

unipolar cells

single cell body and no dendrites

pseudo unipolar cells

cell body in the middle of the axon, make up principal sensory neurons, one end to CNS and other to sensory organs

bipolar neurons

2 extensions, dendrites and axons

multipolar

one axon and many dendrites

why can dendrites change their shape?

due to presence of a protein called actin that contracts or elongates *same used in muscles

3 classifications of dendritic spines

thin, mushroom, stubby

thin spines

grow when a new task is being learned

mushroom spines

formed when thin spines are reinforced by practise aka memory spines

how many pairs of spinal nerves are there?

31

how many neuromeres make up the hindbrain?

12

what are hindbrain’s neuromeres classified as

1 segment closest to midbrain - isthmus

other 11 are called rhombomeres

how many cranial nerves does hte brain have?

10

1 - arises from midbrain, the oculomotor

9 from hindbrain

what is the most prominent nuclei of the brain stem

cranial nerve nuclei

specifically monoamine nuclei, they project to the cerebellum and give rise to descending tracts

what are colliculi and how are they connected to the hindbrain

the hindbrain contains 2 small hillocks of neurons called colliculi

→ relay auditory information

→ play a role in automatic reflex responses when we move our heads/eyes to sudden unexpected sound or object or touch

where is the diencephalon

above the midbrain below cerebrum

what is the diencephalon

consists of structures lying on either side of the fluid filled third ventricle

which ventricle is concintous with the central canal of the spinal cord

4th

what does the nuclear complex consist of

the hypothalamus, epithalamus, the ventral thalamus, the dorsal thalamus, separated by a system of myelinated fibres

do all sensory systems have a thalamic nuclei

except smell

what is the hypothalamic output

neural projections and endocrine hormones

how does the hypothalamus pass signals back and forth betwene the anterior and posterior pitutitary

using neurohyposis and median eminence

what tissue is the anterior pituitary derived from

epithelial tissue

what is the posterior pituitary gland derived from

the hypothalamus

where is hypothalamic endocrine control located

paraventricular nucleus

funciton of paraventricular nucleus

secretion of release factors

where are release factors manufactured

neurosecretory cells, transported in a special vascular network to the anterior pituitary

normal resting membrane potential

-60 to -90 mV

depolarisation

cell becomes less negative

hyperpolarisation

cell becomes more negative

how to maintain RMP?

movement of ions across the two sides of the cell membrane using active pumps, meaning requiring energy to conduct avitiy

MP in AP

to 30-40, then back to -90, before normal over 2 milliseconds

class of epi and norepi

catecholiamines

epi, norepi - which less mass

norepi

where is epi released from

adrenal medulla

where is norepi released from

sympathetic nerve fibres near adrenal glands

function of epi

relax airways and smooth muscles, constrict networks of blood vessels but dilating vessels in muscles and liver, energy production increases with glucose production and fatty acid circulation, increases visual acuity by eye muscle contractions

function of norepi

also involved in energy production, constricts all blood vessels, inc. BP and HR by targeting heart, modulates immune cells, released for attention and concentration

2 types of chemical signalling

synaptic and non synaptic

synaptic chemical signalling

only in neurons using NTs over short distances

non synaptic CS

neurons and non-neuronal cells, using hormones for long or very long distances or local chemical mediators for short distances (apracrine, with adjacent cells) or very short distances (autocrine on to self)

what mass of the brain is the cerebrum

83%

what are the 3 layers of the cerebrum

cortex, white matter, basal nuclei

back block

contains regions that process sensory information

middle block

directed and planned movement

front block

executive function

how many layers of cerebrum

6

upper layers

information is integrated and learning occurs

middle layers

input layers

inner layers

send axons to other brain regions

basal ganglia function

work with substantia nigra to coordinate and make smooth a sequence of behaviours to achieve a target

3 layers of eye

1. sclera - outermost of tough connective tissues whose collagen layer continues forward to form the transparent cornea

2. choroid - intermediate vascular layer that continues to form the ciliary body

3. retina - the innermost layer that holds the receptor cells

myopia

short sightedness, too much refraction and light diverges again

hypermetropia

long sightedness, not enough refraction, light is not focused

role of the iris

regulate light entry through contraction fo the muscles

near response

1. lenses acommondate

2. pupils constrict

3. eyes converge

this is when eyes switch from looking at distant object to near

why decrease/increase light

1. prevent saturation of photorceptors and allow maximum capture in dim light

2. reduce spherical aberration (outer parts of lens distort the image because of too much refraction)

what are chromophores alwways made of

11-cis-retinal which is derived from vitamin A

how GPCR work

activated by stimulus → binds and activates a g protein that can set off a cascade of intrecellular reactions

cyclic GMP

molecule that allows ions to flow into a cell

why cascade system

amplify signal

why rods day no work

cyclic GMP breakdown same as production

foveal vision

only due to cones

non-foveal vision

cones + rods

dif. between foveal and non-foveal vision

1. GAZE

   cones → axial gaze

   rods → universal gaze

   due to location of receptors across retina

2. WAVELENGTH SENSITIVITY

   cones → yes

   rods → no

   types of protein opsin, rods only have one while rods have 3

3. ABSOLUTE SENSITIVITY

   → rods are more sensitive

   → due to efficiency of cascade mechanisms, rods have a more sensitive cascade

4. SPEED

   → cones signal fast events

   → rods signal slow events

   → due to recovery rate

5. ACUITY

   → fovea high acuity

   → non fovea low acuity

   → due to RF size

layers of lateral geniculate nucleus

2 inner - magnocellular, containing large cells

M cells - large cell bodies and dendrites spread widely

4 outer - parvocellular , containing small cells

P cells - small cell bodies, dendrites don’t spread very widely, can be wavelength sensitive