THE NERVOUS SYSTEM

Meet Patel and Auriana Semans AP Biology

General Information

Major components of the nervous system: Central Nervous System (CNS)- made up of spinal cord and

brain Peripheral Nervous System (PNS)- made up of nerves

Neurons- cells that make up the nervous system. They consist of axon, 2 or more dendrites and cell containing nucleus.

Function of the Nervous System The Nervous system has 3 main functions: sensory, integration

and motor

>Sensory: it involves collection information from sensory receptors which monitor internal and external conditions. These signals are then passed down to central nervous system (CNS).

>Integration: it involves processing of many sensory signals passed to CNS. These signals are evaluated, committed to memory, discarded or used for decision making. In other words its combining information from other/different sources and analyzing them to make body run smoothly and effectively.

>Motor- once the network of interneurons is evaluated it releases hormone or moves a part of the body to respond to stimulus.

Central Nervous System

The Central Nervous System regulates our everyday function such as language, emotion, creativity , expression and personality. The Central Nervous System includes the brain and spinal cord.

Spinal cord serves signals between the brain and rest of the body. The function of spinal cord is to connect large of peripheral nervous system to the brain and serve as reflex center. The signal between spinal cord and body is passed through spinal nerves.

Brain is responsible for integrating most sensory information and coordinating body functions. Complex feelings such as emotions or thinking as well as regulation of homeostasis is attributed to the brain. Brain receives its signals from the spinal cord and 12 cranial nerves. Few examples of cranial nerves are:

Optic nerve- carries visual information from eye to the brain.

Facial nerves- makes the muscle of face to make facial expressions.

Contd…..

Both spinal cord and brain consist of

Grey matter- contains cell bodies, dendrites and axon terminals of neurons. Synapse mostly occurs in grey matter of the brain

White matter- made up of axons connecting different parts of grey matter to each other.

The entire CNS is located inside Cerebrospinal Fluid and its essential to CNS as it

1.Absorbs the shocks between the brain and the skull.

2. The brain and spinal cord float within Cerebrospinal fluid which reduces their weight through buoyancy.

3. It helps maintain chemical homeostasis within the nervous system.

Peripheral Nervous System

The main function of Peripheral Nervous System (PNS) is to connect CNS to limbs and organs in the body. It consists of 12 pairs of spinal nerves and 31 pairs cranial nerves that help deliver signals throughout the body.

Peripheral Nervous System is divided into Somatic and Autonomic system.

Somatic Nervous System- its responsible for all voluntary movements as well as processing sensory information that arrives from outside stimuli. Its like passage way from environment to CNS.

Autonomic Nervous System- responsible for carrying internal body functions such as breathing, heartbeat, digestive process etc. In other words it controls subconscious parts of the body.

Contd…..

The Autonomic nervous system has two parts:

Characteristics                Sympathetic                  Parasympathetic

When functioning?         emergencies                       normal/everyday

Digestive system             inhibits/slows down             promotes 

Pupil                                   dilates                                   constricts

Heartbeat                           accelerates                           slows down

Breathing rate                  increases                                slows down

Neurons

There are three basic parts of a neuron: the dendrites, the cell body and the axon. The cell body contains the nucleus and most of the cellular organelles. The dendrites are small tree like structures that pick up stimuli from the environment. The axons send signals onto other neurons or cells in the body.

Types of Neurons

There are 3 types of neurons:

Sensory neurons - send information from the sense organs (outside) to the C.N.S. They have long dendrites and short axons.

Motor neurons - send information from the C.N.S to the muscles. Causing the muscles to move. They have short dendrites and long axons.

Interneurons - connect different neurons together, send information between neurons. They have short dendrites and short axons.

How do Neurons transmit and receive information??

The dendrites receive the information from sensory cells which then is passed down to the cell body where the information is evaluated and on to the axon. Once the information is at axon it travel downs length of axon in form of electrical signal known as action potential.

Once the electrical impulse has reached end of axon it must be transmitted to another neuron or cell through synapse. If neuron is adjoined to the dendrites of another neuron electrical signals are  instantaneously sent allowing signal to continue its path. However in some cases of long distance signaling neurotransmitters are used as they are chemical messengers that are released from axon to cross synaptic gap and bind to receptor sites of other neurons.

Example of synapse using electrical signals as the dendrites of another neuron are adjoined at end of axon so signal can keep flowing through.

References

1. "Nervous System." InnerBody. N.p., n.d. Web. 09 Apr. 2015.

2. Overview of the Autonomic Nervous System." : Autonomic Nervous System Disorders: Merck Manual Home Edition. N.p., n.d. Web. 09 Apr. 2015.

3. Cherry, Kendra. "What Is a Neuron? Building Blocks of the Nervous System." N.p., n.d. Web. 09 Apr. 2015.

4. "Peripheral Nervous System: Definition, Function & Parts | Study.com."Study.com. N.p., n.d. Web. 09 Apr. 2015.

Quiz Questions

1. Which nervous system controls the involuntary movements in body?

2. The nervous system is made up of cells called__________ 3. What kind of neurons transmits impulses 

a. towards the C.N.S.     b. away from the C.N.S 4. Identify the 3 parts of the neuron

5. The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____.

synaptic cleft node of Ranvier internodes synapse synaptic terminal

Answers!!

1. Autonomic Nervous System

2. Neurons

3. a. sensory neurons b. motor neurons

4. a. axon b. dendrites c. nucleus

5. D. Synapse