Week 1 content

Question 1

what are the stages of propagation

Answer 1

1. resting potential - voltage gated sodium and potassossium channels are closed, inside is more negative than outside (-70mv).
2. slow depolarization - local potentials summate to depolarize the membrane. voltage-gated sodium and potassium channels remain closed.
3. fast depolarization - when the threshold is reached, voltage gated sodium channels and sodium rushes in. the membrane quickly depolarizes to a positive membrane potential.
4. repolarization - voltage-gated sodium channels are inactivated. many voltage gated potassium channels open, potassium exists which decreases the overall charge of the membrane.
5. hyperpolarization - voltage gated potassium channels remain open and potassium continues to the leave the axon restoring the membrane potential.

Question 2

what is myelin and its function?

Answer 2

produced by oligodendrocytes in CNS and scwann cells in PNS (both these cell types wrap around the neuron).

myelin acts an insulator and increases speed to conduction along the axon.

Question 3

define Aa, AB, and Ay neurons

Answer 3

all myelinated.

Aa - proprioception, motor.
AB - touch
Ay - motor (from spindles)

Question 4

define AS, B and C neurons

Answer 4

AS and B are myelinated (AS only has a thin layer).

AS - pain, temp and touch.

B - autonomic NS.

C is not myelinated - pain, autonomic NS.

Question 5

neurotransmitters

Answer 5

are chemicals released from the axon terminal and act on the post-synaptic terminal.

inhibitory - binding of the neurotransmitter causes further polarisation os th epost synpatic membrane, moving the membrane away from the threshold and so reducing the chance of an AP occurring (inhibitory effect).

excitatory - binding of the neurotransmitter causes depolarization of the post synaptic membrane, if the membrane reaches threshold then an AP will result.

Question 6

what are converging and diverging neurons

Answer 6

converging - multiple neurons synapse with a single neuron

diverging - single neuron synapses with multiple neurons.

Question 7

briefly explain how contraction of a muscle fiber results

Answer 7

achtlycholine is released from post synaptic terminal and binds with receptor sites of muscle, causing excitation, threshold is reached which leads to contraction of muscle fibre.

Question 8

stages of prenatal development

Answer 8

1. pre-embryonic state (zygote)
2. embryonic stage (embryo)
3. fetal stage (foetus)

Question 9

what happens in the pre-embryonic stage of prenetal development

Answer 9

fertilisation of ovum by sperm occurs from day 0-14

Question 10

what happens in the embryonic stage

Answer 10

once the zygote implants in uterus from day 15 to the end of 8th week.

• Weeks 3 to 8
• All tissues and organs are formed
• Cell proliferation, cell migration, cell differentiation.
• Embryonic disk and neural tube formation (cephalic to caudral), primitive brain and spinal cord formed.
• Heart, muscles, rubs and backbone digestive tract begin to develop, external structures and internal organs form, sense of touch, embryo can move.

Formation of embryonic disc
- Endoderm: gut, liver, pancreas and respiratory system.
- Mesoderm: muscles, skeleton, excretory and circulatory systems.
- Ectoderm: sensory organs, hair, skin and nails and the whole nervous system.

Formation of the neural tube:
- Develops into brain, spinal cord and spine.
- Thickening of ectoderm leads to neural groove at 20 days, edges of neural plate then elevate to neural folds, then neural folds curve upwards during neurulation and forms neural groove.

Question 11

congenital anomalies of the nervous system - neural tube defects.

Answer 11

→ Spina bifida – neural tube doesn’t close properly, due to low folic acid. Failure to develop spinal cord and vertebral canal.
→ Anencephaly – neural tube does not develop at the cephalic end. Results in a failure to develop cerebral hemispheres and cerebellum.

Question 12

what happens in the foetal stage of prenatal development

Answer 12

From end of 8th week until birth.

Question 13

what happens in weeks 13-24 of prental development

Answer 13

Weeks 13-24
o Neurogenesis (generation of new nerve cells)
o Most neurons are present by 24 weeks.
o Major regions of brain develop.
o Eyes sensitive to light, reacts to sound.

Question 14

what happens between weeks 25-38/40

Answer 14

→ Weeks 25-38/40
o Size increases, lungs mature, rapid brain development.

Question 15

define teratogens and give examples

Answer 15

teratogens are substances of conditions that can disturb development of an embryo/foetus.

→ Teratogens are substances of conditions that can disturb development of an embryo/foetus.

o Medications
o Maternal infection s
o Chemicals
o Maternal disorders
o Hypertension
o Substance abuse
o Therapeutic radiation
o Dose
o Heredity
o Combination of negative influences
o Organism age (sensitive period concept)

Question 16

define a sensitive - prenatal

Answer 16

Sensitive period: prenatal
→ Limited time in which a part of the body or behaviour is biologically prepared to develop rapidly.
→ Period of organ differentiation – cells becoming specialised
→ Especially sensitive/receptive to its surrounding environment.

Question 17

define a sensitive - prenatal

Answer 17

Sensitive period: prenatal
→ Limited time in which a part of the body or behaviour is biologically prepared to develop rapidly.
→ Period of organ differentiation – cells becoming specialised
→ Especially sensitive/receptive to its surrounding environment.

Question 18

define neonates

Answer 18

→ Neonate = first 4 weeks after birth
→ Full term infant – 37 weeks
→ All body structures, neurogenesis largely complete.
→ Baby still adjusting to sounds and light environment.
→ Neurologically immature, still developing - myelination and synaptogenesis.