2.2 THE NERVOUS SYSTEM

The body’s communication systems help maintain homeostasis. A stimulus causes a response. Responses can be chemical, cellular, or behavioral. The nervous system responds to stimuli.

The nervous system controls thoughts, movement, and emotion.

The nervous system works quickly, using chemical and electrical signals. interconnected network of cells signals move through cells divided into central nervous system (CNS) and peripheral nervous system (PNS) spinal chord nerves

The nervous system’s two parts work together. The CNS includes the brain, brain stem, and spinal cord. The PNS includes four systems of nerves.

The CNS processes information. The brain has three parts. cerebrum controls thought, movement, emotion

Lobes of the Brain There is a fifth lobe, known as the limbic lobe, that is responsible for emotions

The CNS processes information. The brain has three parts. cerebrum controls thought, movement, emotion cerebellum allows for balance brain stem (reptilian brain) controls basic life functions Brain stem midbrain pons medulla oblongata

The brain stem has three parts. midbrain controls some reflexes pons regulates breathing medulla oblongata controls heart function, swallowing, coughing midbrain pons medulla oblongata

The spinal cord controls reflexes. sensory neuron sends impulse to spinal cord spinal cord directs impulse to motor neuron does not involve the brain See simulation with online textbook interneuron motor neurons sensory neuron

The PNS gathers and transmits information links the CNS to muscles and other organs. The somatic nervous system regulates voluntary movements.

The PNS gathers and transmits information The autonomic nervous system controls involuntary, functions sympathetic nervous system: “fight vs. flight” Involved in all internal adjustments that prepares the body for action or increased levels of stress. parasympathetic nervous system: sends impulses that return a body to “normal” functioning after a period of stress is over, conserves energy

Sympathetic Parasympathetic Fine adjustments made so glands and organs are functioning at levels appropriate to a body at a particular time: Sympathetic Parasympathetic Dilates pupils Inhibits saliva Constricts blood vessels Accelerates heart Bronchi dilate Glycogen converts to glucose Bladder relaxes Constricts pupil Stimulates salivation Dilates blood vessels Reduces heart rate Constricts bronchi Stimulates bile release Contracts bladder

The CNS and PNS pass signals between one another. Sensory receptor generates impulse. PNS passes impulse to CNS. CNS interprets impulse. CNS passes impulse to PNS. PNS stimulates a response.

Basic Organization sensory receptor (sensory input)  integration  (motor output)  effector Sensory Input triggered by stimuli conduction of signals to processing center Integration interpretation of sensory signals within processing centers Motor output conduction of signals to effector cells (i.e. muscles, gland cells)

Nerves Nerves, which carry the electrical impulses to various parts of the nervous system, are made up of a bundles of cells, known as neurons

Neurons are highly specialized cells. A neuron has 3 main parts. cell body contains nucleus and organelles 1 Cell body

Neurons are highly specialized cells. A neuron has three parts. cell body has nucleus and organelles dendrites receive impulses 2 dendrites

Neurons are highly specialized cells. A neuron has three parts. cell body has nucleus and organelles dendrites receive impulses axon carries (transmits) impulses 3 axon

Neurons have other structures to transmit signals. Schwann cell makes up the myelin sheath, which insulates the axon

Neurons have other structures to transmit signals. Schwann cell makes up the myelin sheath, which insulates the axon Nodes of Ranvier – the gaps between the myelin sheath that speed up the process of transmitting impulses.

Neurons have other structures to transmit signals. Schwann cell makes up the myelin sheath, which insulates the axon Nodes of Ranvier – the gaps between the myelin sheath that speed up the process of transmitting impulses. Axon terminal – part through which the impulse leaves. axon terminal

Neurons have other structures to transmit signals. Schwann cell makes up the myelin sheath, which insulates the axon Nodes of Ranvier – the gaps between the myelin sheath that speed up the process of transmitting impulses. Axon terminal – part through which the impulse leaves. synapse gap between the neuron and the next cell. synapse

Types of Neurons Sensory Neuron: detect stimuli and transmit signals to the brain and the spinal cord, which are both made up of interneurons. Interneurons: receive signals from sensory neurons and relay them within the brain and the spinal cord. Process information and pass signals to motor neurons. Motor neurons: pass messages from the NS to other tissues in the body, such as muscles