Mrs: Jackie Reflexes

Spinal reflexes- the brain is not needed theoretically to happen Example of the hand removal from the heat Another example of reflex arcs Bright light stimulates the light sensitive cells of the retina. The nerve impulses in the sensory fibers from these receptors travel through the optic nerve to the brain. In the mid brain the fiber synapse with the relay and motor fibers which carry impulses back through the optic nerve to the sphincter muscle of the iris and stimulate it to contract. THIS REFLEXES HAVE PROTECTIVE FUNCTIONS=INVOLUNTARY ACTIONS

Voluntary Actions Starts in the brain May be the results of an external event Unlike a reflex action it does not happen automatically, you decide whether to carry or not the action The brain sends motor impulses down the spinal cord in the nerve fibers. These make synapses with motor fibers which enter spinal nerves and make connection to the sets of muscles needed to produce effective action

Part I Homework 1. Put the following in the correct order for a simple reflex arc a.impulse travels in motor fiber b. impulse travels in sensory fiber c.effector organ stimulated d. receptor organ stimulated e. impulse crosses synapse 2. Which receptors (sense organ) and effectors are involved in the reflex actions of a. sneezing b.blinking c.contraction of the iris 3. Explain why the tongue may he considered to be both a receptor and an effector organ? 4. Explain whether coughing is a voluntary or reflex action.

Spinal cord Like other parts of the nervous system consist of thousands of nerve cells All the cell bodies apart from the dorsal root ganglia are concentrated in the central region called the grey matter. The white matter consist of nerve fiber. Nerve fiber- filament of cytoplasm runs from the cell body of the neuron Nerve consist of hundreds of nerve fibers together(mixture of sensory and nerve fiber) Spinal cord function Reflex actions involving body structures below the neck Conducting sensory impulses from the skin and muscles to the brain Carrying motor impulses from the brain to the muscles of the trunk and limbs.

Spinal Cord

The brain Parts of the brain Medulla- involve in breathing rhythm, heart rate, swallowing and vasoconstriction or the arterioles. Basically involve reflex actions but are also influence by nerve impulses from other parts of the brain such as the hypothalamus and cerebrum Cerebellum- maintain balance and coordinating movement Cerebrum-largest part of the brain. Consist of two cerebral hemisphere. Concern with intelligence, memory, reasoning, acquired skills and consciousness. Cortex- located in the hemispheres with thousands of multipolar neurones (synapses within the CNS). Hemispheres- command center

The brain: Main Parts

Functions of the brain Receives impulses from all sensory organs of the body As a result of these sensory impulses, it sends off motor impulses to the glands and muscles, causing them to function accordingly In its association centers it correlates the various stimulus from the different sense organs and the memory. The association center and motor areas coordinate bodily activities so that the mechanisms and chemical reactions of the body work efficiently. It stores information so that behavior can be modified to past experience

Homework Part 2 Would you expect synapses to occur in the white matter of grey matter? Explain With which senses are the fore, mid and hind brain mainly concerned?