Fertilzation

Spermatogenesis - what is it

The process of making sperm

Step 1 of spermatogenesis

A spermatogonium undergoes mitosis

What does mitosis of a spermatogonium produce

Another spermatogonium AND a primary spermatocyte

Step 2 of spermatogenesis

The primary spermatocyte undergoes meiosis I

What does meiosis I produce in spermatogenesis

Two secondary spermatocytes

Step 3 of spermatogenesis

Each secondary spermatocyte undergoes meiosis II

What does meiosis II produce in spermatogenesis

Four spermatids in total

Step 4 of spermatogenesis

The spermatids differentiate into four mature sperm cells

Order of cells in spermatogenesis

Spermatogonium then primary spermatocyte then secondary spermatocyte then spermatid then sperm

Why do males never run out of sperm

When spermatogonia divide by mitosis half become primary spermatocytes and half stay as spermatogonia so the supply never runs out

How many sperm come from one primary spermatocyte

Four

Path of sperm 1st structure

Seminiferous tubules

Path of sperm 2nd structure

Epididymis

Path of sperm 3rd structure

Vas deferens

Path of sperm 4th structure

Ejaculatory duct

Path of sperm 5th structure

Urethra

Path of sperm 6th structure

Penis (sperm leaves the body)

Full path of sperm in order

Seminiferous tubules then epididymis then vas deferens then ejaculatory duct then urethra then penis

Three male glands to know

Seminal vesicle and prostate gland and bulbourethral gland

Seminal vesicle - what it makes

Fluid with fructose and prostaglandins

Seminal vesicle - what fructose does

Gives energy to sperm

Seminal vesicle - what prostaglandins do

Cause the uterus to contract

Seminal vesicle - amount of semen

About 60% of semen volume

Prostate gland - what it makes

Fluid with citrate and anticoagulant enzymes

Prostate gland - what citrate does

Is a nutrient for sperm

Prostate gland - what anticoagulant enzymes do

Keep semen from clotting

Bulbourethral gland - what it makes

Mucus

Bulbourethral gland - what the mucus does

Neutralizes acidic urine in the urethra

Bulbourethral gland - when it releases

During arousal before ejaculation

Where do the seminal vesicles join the pathway

At the vas deferens to form the ejaculatory duct

Where do the prostate and bulbourethral glands empty

Into the urethra

Where are sperm made

In the seminiferous tubules (not the glands)

Oogenesis - what is it

The process of making an egg

Oogenesis step 1 (before birth)

Primordial germ cells undergo mitosis and make oogonia

Oogenesis step 2

Oogonia undergo mitosis and make primary oocytes in the ovary

Where do primary oocytes pause before birth

Prophase I of meiosis I

How long do primary oocytes stay paused

Until puberty (years)

What happens at puberty in oogenesis

Meiosis I continues and finishes

What does meiosis I produce in oogenesis

Two unequal cells - a big secondary oocyte and a tiny first polar body

How does a primary oocyte become a secondary oocyte

By completing meiosis I

Where does the secondary oocyte pause

Metaphase II of meiosis II

What happens to the first polar body

It disintegrates

What is a polar body

A tiny leftover cell made when the division is unequal

Where does the secondary oocyte go after ovulation

The oviduct

What happens if no sperm enters the oocyte

It disintegrates

What triggers the egg to finish meiosis II

A sperm entering

What does meiosis II produce in oogenesis

One large fertilized cell (zygote) and a tiny second polar body

First polar body comes from

Meiosis I

Second polar body comes from

Meiosis II

How many times does oogenesis pause

Twice - prophase I and metaphase II

Female reproductive structures to know

Ovary and oviduct and uterus

Ovary - function

Where the egg is released from

Oviduct - function

Where the egg enters after leaving the ovary and travels along

Uterus - function

Where the egg ends up

Path of the egg in order

Ovary then oviduct then uterus

Continuous conduction - axon type

Unmyelinated axons (gray matter)

Saltatory conduction - axon type

Myelinated axons (white matter)

Continuous conduction - how the signal moves

A smooth wave of depolarization

Saltatory conduction - how the signal moves

The signal jumps from node to node

Continuous conduction - where depolarization happens

Every spot along the axon depolarizes and repolarizes

Saltatory conduction - where depolarization happens

Only at the nodes of Ranvier

Does continuous conduction need myelin

No

Does saltatory conduction need myelin

Yes - it requires the myelin sheath

Continuous conduction - speed

Slower

Saltatory conduction - speed

Faster than unmyelinated

Continuous conduction - energy use

Less energy efficient

Saltatory conduction - energy use

More energy efficient

Which conduction occurs in gray matter

Continuous conduction

Which conduction occurs in white matter

Saltatory conduction

Which conduction is faster

Saltatory conduction

Which conduction is more energy efficient

Saltatory conduction

Myelin sheath

Fatty insulation around the axon that is rich in myelin

What makes myelin in the CNS

Oligodendrocytes

What makes myelin in the PNS

Schwann cells

Internodes

Regions covered by myelin with no depolarization

Nodes of Ranvier

Gaps with no myelin and lots of Na+ and K+ channels where depolarization happens

Where does depolarization occur in a myelinated axon

Only at the nodes of Ranvier

What does saltatory mean

Jumping (the signal jumps node to node)

What do both conduction types share - signal

A series of action potentials along the axon

What do both conduction types share - direction

Unidirectional (one direction)

What do both conduction types share - refractory period

The signal stays behind the refractory period

What do both conduction types share - trigger

A voltage shift in one region triggers channels further down the axon

What happens if the axon center is artificially stimulated

The action potential goes in two directions

Why does the signal only travel one way normally

The refractory period behind it

What happens if myelin is damaged

Saltatory conduction is disrupted and the signal is slower

Memory line - continuous

Unmyelinated and smooth and slow

Memory line - saltatory

Myelinated and jumps and fast

Memory line - both

Action potentials moving one way