Male reproductive system

Let´s start to study reproduction.

Living organisms reproduce sexualy or asexualy. Therefore, we say that there are two types of reproduction.

  1. Act: Use information from the text book to build a comparison table between sexual and asexual reproduction.

Humans reproduce sexualy.

2.  Watch this video to learn about the MALE REPRODUCTIVE SYSTEM.

3. Act: Summarize the functions of each of the organs which are part of the male reproductive system. Take a look at THESE SLIDES !

Penis: This is the male organ used in sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped part at the end of the penis. The glans, also called the head of the penis, is covered with a loose layer of skin called foreskin. The opening of the urethra is at the tip of the penis. The glans of the penis also contains a number of sensitive nerve endings. The penis delivers semen to the female during intercourse and has the urethra, which is used to transport semen and urine.

Testicles: these are oval organs that lie in the scrotum Men have two testes. The testes are responsible for making testosterone and for generating sperm.

Scrotum: This is the sac of skin that hangs behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum acts as a climate control system for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than body temperature.

Urethra: the tube that carries urine from the bladder to outside of the body. It has the additional function of ejaculating semen when the man reaches orgasm.

Bulbourethral glands: pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a slippery fluid that serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra.

Prostate gland: The prostate gland is a structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra runs through the center of the prostate gland.

Epididymis: a long tube that rests on the backside of each testicle. It transports and stores sperm cells that are produced in the testes. It also is the job of the epididymis to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization.

Seminal vesicles: pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move. The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fluid, or ejaculate.

Ejaculatory ducts: These are formed by the fusion of the vas deferens and the seminal vesicles. The ejaculatory ducts empty into the urethra.

4. State the components and the function of semen.

Semen is a greyish white bodily fluid that is secreted by the gonads of male animals. It carries sperm or the spermatozoa and fructose and other enzymes that help the sperm to survive to facilitate successful fertilization.

The semen has:

  • fructose
  • ascorbic acid
  • zinc
  • cholesterol
  • protein
  • calcium
  • chlorine
  • blood group antigens
  • citric acid
  • DNA
  • Magnesium
  • vitamin B12
  • phosphorus
  • sodium
  • potassium
  • uric acid
  • lactic acid
  • nitrogen
  • other nutrients

Its function is to unite one half of the man’s DNA with one half of the woman’s, creating a complete set of DNA in the fertilized egg, which grows into a human fetus.

5. Make a large labelled drawing of a sperm cell and state how the structure is adapted to its function. (Do not add a picture).

Nervous system: neurones and synapse

All mammals have a CENTRAL NERVOUS SYSTEM and a PERIPHERAL NERVOUS SYSTEM. The CNS is made up of the brain and the spinal cord. The peripheral nervous system is made up of nerves and receptors.

The NEURONS are special cells which coordinate the messages travelling through the nervous system.

  1. ANATOMY OF A NEURON: Watch THIS video!

Act: State how the structure of a neuron is related to the function.

  • A neuron has three main functions: receive signals, integrate incoming signals and communicate signals to other neurons or muscles or glands. The  structure of a neuron is related to the functions since the first two neuronal functions generally take place in the dendrites. A single neuron may have a lot of dendrites, so it can communicate with thousands of other cells but only one axon which passes the nerve impulses on to other cells.
  • And a long axon to send nerve impulses accross long distances.

 

  1. TYPES OF NEURONS: Read “overview of neuron structure and function   from HERE
  • Act: Make a labelled drawing of each of the three types of neurons, motor, sensory and relay, and state their functions.

Sensory neurons: get information about what’s going on inside and outside of the body and bring that information into the CNS so it can be processed.  

Motor neurons: get information from other neurons and convey commands to your muscles, organs and glands.

Relay neurons:  carry messages from one part of the CNS to another.

YOU SHOULD MAKE THE DRAWING

 

  1. SYNAPSE:
  • Act: Post a short video explaining synapse.
  • Act: Describe in your own words how nerve impulses are transmitted from neurone to neurone.

 

https://www.youtube.com/watch?v=Iws8w6NpsGg

 

  • The video shows us that most of the communication between the neurons occurs in a structure called Synapse. There is a neuron called “Presynaptic Neuron” (where the signals are initiated) On the other hand,  the other neurone (the one who receives the message) is named “Postsynaptic Neuron”. The video also explains that the two neurons are separated by the synaptic cleft. Chemical signals are present in the Presynaptic Neuron and packed into vesicles. When that neuron receives an electrical signal, it gets excited and leads the vesicles release their contents into the synaptic cleft. One they are  in the synaptic cleft, the receptors interact with the neurotransmitters and is able to catch the information. Because of this the neurotransmitter molecules are cleaned away from the synaptic cleft.

 

  • The transmission of a nerve impulse along a neuron from one end to the other occurs as a result of electrical changes across the membrane of the neuron. The membrane of an unstimulated neuron is polarized.

Virtual period: sex hormones and puberty

Sex hormones are responsible of the most dramatic changes that occur in the body. They control puberty, egg and sperm production, pregnancy, birth and lactation.

  1. Read the information about Puberty HERE.
  2. State the female and male hormones which are responsible for the development of the secondary sexual characteristics
  3. Build a comparison table between the changes that occur in male and female after puberty.
  4. Search in the internet and summarize the site of production and effects of the following sex hormones:

– FSH, LH, oestrogen, progesterone, oxytocine, Hcg, prolactine and testosterone.

5. The chart shows the ages at which the changes associated with puberty take place in boys and girls. Answer questions a, b, c, d and e.

(a) What is the most common age at which boys undergo the changes of puberty?

(b) If a girl had not started menstruation by the age of 15, would this be cause for concern?

(c) Which two features of puberty show the greatest range in the times at which they  occur.

 

(d) Is it unusual for a girl of 9 years to start her menstrual periods?

(e) On average, is it boys or girls who first show the onset of puberty?

Answers:

2. The female hormones responsible for the development of the secondary sexual characteristics are; oestrogen and progesterone. This hormones make women breast grow, public hair grow and develop wide hips. The male hormone responsible for the development of the secondary sexual characteristics is testosterone. These hormones are stimulated by Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH) . This hormone makes the men body hair grow, the voice break and the muscles growth increase.

3.

4.

  • FSH: It is produced by the pituitary gland and it:
    • Causes an egg to mature in an ovary.
    • Stimulates the ovaries to release the hormone oestrogen.
  • LH: It causes the mature egg to be released from the ovary.
  • Oestrogen: It is secreted by the ovaries and it:
    • Stops FSH being produced – so that only one egg matures in a cycle.
    • Stimulates the pituitary gland to release the hormone LH.
  • Progesterone: It is secreted by ovaries. It maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.
  • Oxytocin: It is a hormone produced by the hypothalamus and secreted by the pituitary gland. This important hormone plays a crucial role in the childbirth process and also helps with male reproduction.
  • HCG: It is a hormone produced by the placenta after implantation. Human chorionic gonadotropin interacts with the LHCG receptor of the ovary and promotes the maintenance of the corpus luteum during the beginning of pregnancy.
  • Prolactin: It is a hormone produced in the pituitary gland, named because of its role in lactation. It also has other wide-ranging functions in the body, from acting on the reproductive system to influencing behaviour and regulating the immune system.
  • Testosterone: It is a hormone that is responsible for many of the physical characteristics specific to adult males. It plays a key role in reproduction and the maintenance of bone and muscle strength.

5.

a. The most common age is when they are 12.

b. No, the avarage age is between 12 and 13 years old. But it is normal.

c. The first menstrual period and the growth on breast and hair.

d. No, it is normal, but not very common.

e. Girls are usually developed first.

Pupil reflex

PUPIL REFLEX

In pairs, add a video which shows the pupil reflex in your eyes.

Using your reflex actions´knowledge , sketch the sequence of the pupil reflex. State the stimulus, receptors, coordinator, effector, effect, response and all the neurones involved.

Stimulus —> receptors —> coordinator —> effector —> effect

Bright light —> cones —> brain —> muscles of the iris —> effect (circular muscles contract, radial muscles relax) —> response pupil constricts

Dim light —> nods —> brain —> muscles of the iris —> effect (circular muscles contract, radial muscles relax) —> response —> pupil dilates

What is the importance of this reflex?

The importance of the pupil reflex is controling the amount of light to prevent the retina from gettting damaged.

Booklet act: COMPLETE questions 1 b and c on page 9.

Biology Virtual period: adrenaline ADH

* Raises blood sugar levels by stimulating the liver to change glycogen into glucose
* Causes fatty tissue to release fat into the blood
* Increases the heart rate
* Increases blood flow to the muscles
* Reduces blood flow to the skin and the intestines
* Widens the bronchioles
* Dilates the pupils

It can be
– Under stress
– Under pressure
– In response of a vigorous sudden action

2. Flow chart:
When there is too little water in the body:
– Hypothalamus
– Pituitary
– Kidneys
– Urine becomes less in volume and more concentrated.

When there is too much water in the body.
– Hypothalamus
– Pituitary  (production of ADH will stop)
– kidneys will not save  much water
– Urine becomes dilute and of greater volume
– Level of water in the blood then begins to fall towards the ideal level.

3.