Chapter 2Chapter 2

Exploring the Nervous System

Anatomical ViewsAnatomical ViewsHorizontal section

- Shows structures viewed from above

Sagittal section - Divides structures into right and left parts

Coronal section - Shows views from the front

Anatomical DirectionsAnatomical DirectionsAnatomical directions are used for

locating structures with the body:

• Anterior - toward the front• Posterior - toward the rear • Ventral - toward the belly• Dorsal - toward the back• Rostral - toward the head• Caudal - toward the tail• Medial - toward the midline• Lateral - away from the midline• Superior - above a structure• Inferior - below a structure

The Importance of the Nervous The Importance of the Nervous SystemSystem

1) Detect stimuli in the environment2) Determine the significance of the

environmental stimuli3) Make a decision based on the stimuli4) Execute a response

Organization of the Nervous System:Organization of the Nervous System:Two Major DivisionsTwo Major Divisions

Peripheral Nervous System (PNS) Detects environmental information

inside and outside the body, which is transmitted to the CNS

Executes responses to stimuli Central Nervous System (CNS)

Recognizes and analyzes information from the PNS

Makes and transmits decisions to glands, organs, and muscles for execution

Cells of the Nervous Cells of the Nervous System:System:

Nerve cells – neurons perform the information processing and communication functions of the nervous system

Glial cells - supportive cells in the nervous system. The glial cells surround neurons and provide support for and insulation between them. 

Cells of the Nervous System: Cells of the Nervous System: NeuronsNeurons

Perform information processing and communications functions of the nervous system

Consist of three major parts: 1. Soma - contains nucleus, mitochondria,

and ribosomes2. Dendrites - portions of the neuron that

transmit information toward the cell body3. Axon - a structure on the neuron which

transmits information away from the cell body

Cells of the Nervous System:Cells of the Nervous System:TerminologyTerminology

Groups of neurons form four functional groups:A collection of axons

Nerve – in the Peripheral Nervous System (PNS) Tract – in the Central Nervous System (CNS)

A collection of cell bodies Ganglion – within the PNS Nucleus - within the CNS

Cells of the Nervous System:Cells of the Nervous System:Functional Types of NeuronsFunctional Types of NeuronsSensory neurons - carry

information to the CNSInterneurons - connect sensory

and motor neurons or communicate with other interneurons

Motor neurons - carry information from the CNS to muscles, organs, and glands to control their functioning.

PhysicalPhysicalTypes ofTypes ofNeuronsNeurons

Cells of the Nervous System:Cells of the Nervous System:Types of SynapsesTypes of Synapses

Axodendritic - the axon synapses with dendrites of another neuron

Axosomatic - the axon synapses with the cell body of another neuron

Dendrodendritic synapse - occurs when the dendrites of one neuron synapses with the dendrites of another neuron

Axoaxonic synapse - the axon of one neuron synapses with the axon of another neuron

Neuromuscular junction - the axon synapses with a muscle

Cells of the Nervous System:Cells of the Nervous System:Glial CellsGlial CellsGlial cells

• One-tenth the size of neurons• Ten times as numerous as neurons

Types of Glial cells• Astrocytes - provide physical support to

neurons, nourishment and other functions. • Microglial cells - remove debris• Oligodendrocytes - produce myelin which

covers the axons of neurons in CNS• Schwann cells - produce myelin which

covers the axons of neurons in PNS

MyelinationMyelination

Organization of the Nervous Organization of the Nervous System:System:The Peripheral Nervous SystemThe Peripheral Nervous SystemDetects internal and external

environmental information; relays information to CNS

Executes CNS’ decisions in muscles, glands and organs

Spinal nerves and Cranial nervesPeripheral Nervous System includes:

Somatic Nervous System - Includes both sensory and motor systems

Autonomic Nervous System - Regulates the internal environment

The Peripheral Nervous The Peripheral Nervous System: System: Somatic Nervous Somatic Nervous SystemSystemEnables us to interact with the physical

environment• Afferent neurons – transmit messages from

sensory receptors to the CNS• Efferent neurons – transmit messages from

the CNS to skeletal muscle• Spinal nerves – 31 pairs of nerves that

send messages to/from the brain thru the spinal cord

• Cranial nerves – 12 pairs of nerves that link sensory receptors in the head directly to the brain and the brain to certain muscles

Cranial NervesCranial Nerves

The Peripheral Nervous The Peripheral Nervous System:System:Autonomic Nervous SystemAutonomic Nervous SystemPrimarily efferent neuronsControls internal environment -

glands and internal organsConsist of two parts that are

typically antagonistic:• Sympathetic • Parasympathetic

The The AutonomiAutonomic Nervous c Nervous SystemSystem

Organization of the Nervous Organization of the Nervous System:System:The Central Nervous SystemThe Central Nervous System Recognizes and analyzes information

received from the PNS Makes and transmits decisions to

glands, organs, and muscles for execution

Central Nervous System includes: Spinal cord - responsible for limited

analysis and decision making, transmits information to and from the brain.

Brain - responsible for analyzing sensory information and making appropriate responses to it.

The Protective Features of The Protective Features of the Central Nervous Systemthe Central Nervous System

Protecting the spinal cord• Vertebral Column - outer bony

covering that encases the spinal cord

Protecting the brain • Skull - outer bony covering that

encases the brain• Ventricular system

Meninges protects both• Dura matter• Arachnoid matter• Pia mater

The Central Nervous System: The Central Nervous System: Spinal CordSpinal Cord

• Serves as a conduit to and from the brain• Controls spinal reflexes

The Central Nervous System: The Central Nervous System: The BrainThe BrainThree main functions:

• Recognizing stimuli detected by the PNS• Analyzing the information• Initiating the appropriate response

Three main areas:• Hindbrain• Midbrain• Forebrain

The Brain: The HindbrainThe Brain: The HindbrainMyelencephalon

Medulla oblongata, which controls basic life functions

Metencephalon Pons - a “bridge” for fibers passing from

one side of the brain to the other. Sensory fibers, fibers from the cortex to cerebellum, and fibers that relay information on sleep, arousal and dreaming pass through it.

Cerebellum - involved in the development and coordination of movement

• Reticular formation Involved in arousal, begins in the medulla

and extends to other areas of the brain

The HindbrainThe Hindbrain

The Brain: The MidbrainThe Brain: The Midbrain

MesencephalonTectum - relays visual and auditory

information and controls simple reflexes, eye and ear orientation movements

Tegmentum -• substantia nigra - integration of

voluntary movements• red nucleus - controls basic body

movements• reticular formation - controls arousal

and consciousnessBrain stem = midbrain + hindbrain not

including the cerebellum

Diencephalon• Epithalamus - contains habenula

(olfactory functions) and pineal gland• Thalamus - major relay station for

sensory information• Hypothalamus - detects need states,

controls the autonomic nervous system, and controls pituitary hormone production and release

• Pituitary - regulates other glandular activity of the body; often called the “master gland”

The Brain: ForebrainThe Brain: Forebrain

The DiencephalonThe Diencephalon

Telencephalon

Limbic System The limbic system is a group of

structures surrounding the brain stem. The limbic system structures include

the amygdala, cingulate gyrus, and hippocampus.

Governs emotions such as anger, fear, and happiness, and is involved in the storage and retrieval of memories.

The Brain: Forebrain The Brain: Forebrain

The Limbic SystemThe Limbic System

The Brain: Forebrain The Brain: Forebrain TelencephalonBasal Ganglia - have widespread

connections to the cortex and forebrain and are involved in the initiation of voluntary movements, maintaining muscle tone and posture

The Brain: ForebrainThe Brain: Forebrain

TelencephalonCerebral Cortex - the convoluted outer

layer of the forebrain that processes sensory information, controls thinking, decision making, stores and retrieves memory, and initiates motor responses

The cortex is divided into two hemispheres connected by the corpus callosum and each hemisphere has four lobes

The Cerebral The Cerebral CortexCortex

The Brain: The Brain: Lobes of the Cerebral CortexLobes of the Cerebral CortexOccipital lobe - primary function is the

analysis of visual informationParietal lobe - The anterior portion

analyses sensory information such as pain, pressure and body position. The posterior portion is involved in spatial perception.

Temporal lobe - includes the primary auditory cortex, a visual area and language centers

The Brain: The Brain: Lobes of the Cerebral CortexLobes of the Cerebral CortexFrontal lobe -

Broca’s area - area for programming and sequencing of motor movements for speech production

Prefrontal cortex - controls complex intellectual functioning such as planning and sequencing of behavior.

Motor cortex - area of the frontal lobe anterior to the central sulcus.

Representation of body parts Representation of body parts in the somatosensory cortex in the somatosensory cortex and motor cortexand motor cortex