Lab 8 Human Sensory Systems

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Human Sensory Systems

Objectives
·Describe how sensory receptors communicate to the central nervous system. ·Describe receptors that detect temperature, pain, touch and pressure, muscle length and tension, and blood pressure. ·Describe the nature of vision in terms of its stimulus on the function of rod and cone cells.

Introduction

The function of the brain is to convey messages to different parts of the body. Messages are conveyed from a nerve cell to another nerve cell, muscle cell, or a gland. The messages are in the form of electrical signals called neurotransmitters. Neurotransmitters are chemicals that are released from a nerve cell that relay a message. Examples of neurotransmitters are acetylcholine, norepinephrine, dopamine, and serotonin. Acetylcholine stimulates voluntary movement of the muscles and norepinephrine stimulates wakefulness or arousal. Dopamine stimulates voluntary movement and emotional arousal and serotonin memory, emotions, wakefulness, sleep as well as temperature regulation.

Nerve cells, neurons, are found in the brain and the spinal cord. They consist of the cell body (soma) which contains the nucleus. Nerve cells also have extensions that branch out from the cell body called the dendrites. The dendrites are the portion of a nerve cell that receives a message. The axon is a long structure that extends out from the cell body, in the opposite direction of the dendrites. It is covered with a myelin sheath. The sheath is an insulator that enables a message to travel down an axon, away from the cell body, very quickly. Schwann cells are cells that form the myelin sheath. Also, there are gaps between the myelin sheath that are not insulated. The gaps are called Nodes of Ranvier. A message traveling down an axon will eventually reach the end of a nerve cell, which is called an axon terminal. The axon terminal releases neurotransmitters into a gap that occurs before the receiving cell. The space between the presynaptic cell (signaling cell) and the postsynaptic cell (receiving cell) is called a synaptic cleft.

When a message is conveyed, an action potential can occur. The resting potential of a nerve cell is approximately -70 mV (millivolts). When a neurotransmitter triggers an action potential, sodium voltage gated channels open and allow sodium (positively charged) to diffuse into the cell. The diffusion of sodium causes the inside of the cell to obtain a positive charge. When the inside of the cell reaches +30 mV, the sodium voltage gated channels close preventing any additional sodium to diffuse into the cell. Next, the potassium voltage gated channels open and enable potassium to diffuse out of the cell. This allows the inside of the cell to return to its original negative charge.

Laboratory Activities

Exercise 1: Understanding the Human Brain

You have been entrusted with the care and feeding of the most extraordinary and complex creation in the universe. Home to your mind and personality, your brain houses your cherished memories and future hopes. It orchestrates the symphony of consciousness that gives you purpose and passion, motion and emotion.

Go to, http://www.alz.org/alzheimers_disease_4719.asp, which is sponsored by the Alzheimer’s Association and take a tour of the brain. Click on “Start Tour”.

Questions: Understanding the Brain

1.What is the texture of the brain?
Texture similar to firm jelly
2.Name the general function of each main brain part:

Cerebrum – remembering, problem solving, thinking, and feeling.

Cerebellum – controls coordination and balance

Brain Stem – connects the brain to the spinal cord and controls automatic functions (breathing, digestion, heart rate, etc)

3.Supply Lines: What percent of energy and oxygen carried throughout your body will the brain use when you are thinking hard? 50% of the fuel and oxygen

4.The Cortex: “Thinking Wrinkles”: Explain the concept of cortex mapping. Each area of the cortex...
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