option a Flashcards
most cells in brain are __ cells
glial
what are neurons produced by and what is this process called
progenitor neuroblasts via neurogenesis
The neural tube contains multipotent neuronal stem cells which can differentiate to form the different types of nerve cells - neurons and glial
whats filipodia
an axon has a growth cone at its tip that contains highly motile growth filaments
describe growth of axon
extension of these filipodia causes the expansion of the internal cytoskeleton within the growth cone – resulting in growth
The direction of this expansion is controlled by chemical stimuli released from surrounding cells
These cells may release chemoattractant signals (grow towards) or chemorepellant signals (grow away)
Using these molecular guidance signals, axon growth cones may navigate long distances to reach specific targets
how does light move in eye
two types of photoreceptors (rods and cones) convert light stimuli into electrical nerve impulses
These nerve impulses are transmitted via bipolar cells to ganglion cells, whose fibres from the optic nerve tract
The photoreceptors line the rear of the retina (adjacent to the choroid), meaning light passes through the other cell layers
how do we hear
The external part of the ear is called the pinna, whereas the internal part of the ear is divided into three sections
The outer ear contains the auditory canal, which channel sound waves to the tympanic membrane (or eardrum)
The middle ear contains three small bones called the ossicles, which transfer vibrations to the oval window
The inner ear consists of the cochlea and semicircular canals, as well as a round window which dissipates vibrations
The cochlear converts sound stimuli into electrical nerve impulses, which are transmitted via the auditory nerve to the brain
explain cochlea implants
Cochlear implants consist of two parts – an external part (microphone / transmitter) and an internal part (receiver / stimulator)
The external components detect sounds, filter out extraneous frequencies and then transmit the signals to the internal parts
The internal components receive the transmissions and produce electrical signals via electrodes embedded in the cochlea
The electrical signals are then transferred via the auditory nerve to be processed by the brain
explain red green colour blindness
there are three different types of cone cells, each of which absorbs different wavelengths (trichromatic: red, green, blue)
The genes responsible for producing red or green photoreceptors are located on the X chromosome (sex-linked)
If either of these genes are mutated, red and green wavelengths cannot be distinguished
As these genes are recessive and located on the X chromosome, red-green colour-blindness is more common in males
Red-green colour-blindness can be diagnosed using the Ishihara colour test
describe vestibular system
Within the semicircular canals are gelatinous caps called cupula, which are embedded with numerous hair cells
When the head moves, the fluid in the semicircular canals (endolymph) follows the direction of movement (due to inertia)
This fluid movement exerts pressure on the hair cells embedded in the cupula, triggering nerve impulses
There are three semicircular canals at 90º angles to one another, allowing head movement to be detected in all three planes
The brain integrates information from the semicircular canals in each ear in order to identify head position and movement
why is neural migration important
This migration process is critical for the development of brain and spinal architecture
differentiate between sympathetic vs parasympathetic
Sympathetic nerves release noradrenaline (adrenergic) to mobilise body systems (‘fight or flight’ responses)
Parasympathetic nerves release acetylcholine (cholinergic) to relax body systems and conserve energy (‘rest and digest’)
Sympathetic Responses (‘Fight or Flight’)
Decreases salivary release and blood flow to the gut in response to swallowing
Increases ventilation rate and dilates airways in response to a reduction in blood pH (caused by increased levels of CO2)
Increases heart rate by raising the normal sinus rhythm of the pacemaker of the heart
Parasympathetic Responses (‘Rest and Digest’ / ‘Feed and Breed’)
Increases salivary release and blood flow to the gut in response to swallowing
Lowers ventilation rate and constricts airways in response to an increase in blood pH (caused by lower levels of CO2)
Reduces heart rate (via vagus nerve) by lowering the normal sinus rhythm of the pacemaker of the heart
brocas vs wernicke area?
broca - Function: Responsible for speech production and language expression. It controls the muscles involved in speaking and helps formulate grammatically correct sentences
wernicke - Damage Effect (Wernicke’s Aphasia): Damage to Wernicke’s area impairs language comprehension. People with Wernicke’s aphasia can speak fluently, but their speech is often nonsensical or lacks meaning, as they have difficulty understanding both their own speech and others’
parietal lobe define
The parietal lobes help interpret feeling, known as sensory information. The lobes process taste, texture and temperature.
