Chapter 24 Regulation

Why do you respond to changes around you? Your responses are controlled by your nervous and endocrine system. Together these 2 systems regulate or control, all of your body’s responses.

Nervous system This system detects and responds to changes inside and outside of your body. How does the nervous system do all of this? 1.The nervous system receives information about the environment or other parts of the body. 2.Then it interprets the information. 3.Finally it responds to the information.

Nervous System 1.Peripheral Nervous System (PNS) – Sensory Neurons – Motor Neurons – Associative Neurons 2.Central Nervous System (CNS) – Brain – Spinal Cord

Peripheral Nervous System (PNS) Neurons = nerve cells – They are the basic unit of structure and function in the PNS. – Their job is to carry messages.

Parts of a neuron Cell body: contains the nucleus and most of the cytoplasm Dendrite: carry messages from other neurons to the cell body Axon: a long thin fiber extends from the cell body that carries messages away to another neuron.

Different kinds of neurons Sensory neurons: carry messages from the sense organs to the spinal cord and brain. Motor neurons: carry messages from the brain and spinal cord to muscles or glands. Associative neuron: connect sensory neurons and motor neurons.

What kind of messages do neurons carry? Impulses are sent from one neuron to the next – They are tiny jolts of electrical chemical energy.

Central Nervous System (CNS) Brain = control center 3 parts – Cerebrum – Cerebellum – Medulla

Cerebrum This is the large upper portion of the brain It controls movement and speech Interprets information from the sense organs Cerebrum controls many functions associated with intelligence (thinking, reasoning, and memory)

Each half controls activities of the opposite side of the body.

Which half of the brain do you think is dominant in people who are left handed? Right side of the brain

Cerebellum This portion of your brain is found at the back of your head beneath the cerebrum and is much smaller. All motor nerve impulses that begin in the cerebrum pass through the cerebellum. The cerebellum adjusts the impulses so that your movements are coordinated. It also helps you maintain balance.

Medulla Nerves from the cerebrum and the cerebellum form a thick stalk called the brain stem at the base of the skull. The medulla is the lower part of the brain stem, which connects the brain to the spinal cord. It controls many involuntary actions (digestion, breathing, blood pressure, and heart rate)

CNS – Spinal Cord The spinal cord is made of many nerves that extend from the medulla all the way down the back. All sensory and motor nerves found below the neck pass through the spinal cord on their way to the brain. 31 pairs of nerves extend from the spinal cord. – These nerves branch many times and go to specific parts of the body.

Nerve Pathway Synapse : gap between the dendrite of 1 neuron and the axon of another. Reflex: automatic response to stimuli. – Although the brain controls most responses it doesn’t control reflexes – Spinal cord controls reflexes Ex: touching a hot pan

Nerve Pathways

Why is a reflex reaction followed by an “ouch”? While impulses are traveling along the reflex arc the spinal cord also sends messages to the brain. Once the brain receives the message and interprets it, it sends messages to the pain receptors in your hand.