The central nervous system

The central nervous system is made up of the brain and spinal cord.

And the peripheral nervous system is made up of nerves and receptors.

The CNS is made up of neurons that coordinate the messages traveling through the nervous system.

The three types of cells, neurons are:

  • The sensory neuron
    Transmit impulses inwards from sense organs to the CNS

  • Motor neurone
    Transmitting impulses from the CNS to muscles and glands elsewhere in the body

  • Relay neurone
    Transmit the electrical impulses generated by the stimuli to other nerves.

Continuing our studies of the nervous system, here it’s a video showing a reflex act.

stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response

In this case, the stimulus is the temperature, the receptors are the thermal receptors in your skin, the effectors are the muscle contraction, the response when the arm bends and the coordinator is the spinal cord.

Biology activity pag. 177

In our biology class, we have been studying coordination and response.


a) In which direction does this synapse allow a nerve impulse to travel?

The nerve impulse travels from the left to he right as the vesicles release the neurotransmitter into the synaptic cleft. Then the neurotransmitters attached to the receptor moleculed in the relay neurone.

b) Describe the roles of the parts labelled A and B in transmitting a nerve impulse from one neurone to the next.

The vesicles contain the neurotransmitters.

The receptors receive the neurotransmitters and trigger a nerve impulse in the relay neurone until it reaches the next synapse.

c) Suggest the role of the mitochondria shown in the diagram.

The mitochondria is where respiration takes place and where energy is released for the neurone to transmit nerve impulses and then the receptors.

Pupil reflex

Pupil reflex:




Stimulus: bright light

Receptor: retina (cones)

(Sensory neurones in the optic nerve)

Coordinator: brain (relay neurone)

Effector: muscles in the iris (motor neurone) (circular muscle contracts and the radial muscle relaxes)

Response: adjust in the size of the pupil, gets smaller




Stimulus: dim light

Receptor: retina (rods)

Coordinator: brain (relay neurone)

Effector: muscles in the iris (radial muscles contract and the circular muscles relax)

Response: adjust in the size of the pupil, it dilates/ widens, to protect the retina.


The circular muscles & radial muscles: antagonistic muscles

They control the amount of light reaching the retina to prevent the damage of photoreceptors.

← Revision Unit 1Trabajo Práctico FisicoQuímica → Food test for Starch, Reducing Sugars and Proteins

With Male we did investigations in the lab to see if milk had reducing sugars, proteins and starch. This are my results.

Reagent               (-)                     (+)

Sample A Test for starch Iodine Solution Brown Blue/Black
Sample B Test  for Proteins Biuret Solution Blue Purple
Sample C Test for Reducing Sugars Benedict Solution Blue Orange
Sample Reagent Colour before invest. Colour after invest. conclusion
A Iodine solution Yellow Brown Yellow brown There is no starch present in milk.
B Biuret solution Blue Purple Proteins are present in milk
C Benedict solution Blue Orange/Yellow Reducing sugras are present in milk.


Movement in and out of cells

During our biology class we studied movement in and out of cells, Diffusion, Osmosis and Active Transport. We used this website to understand the different processes, completed the games and made a comparative chart for the different movements.

Type of molecules Water Ions, gases, other molecules
Concentration gradient Down a water potential. High to low Down a concentration gradient. High to low Against concentration gradient
Energy NO NO YES
Carrier NO NO YES