The Nervous System Structures and Processes Central Nervous System Peripheral Nervous System

Structures and Processes Homeostasis Organization Cells of the Nervous System The Nerve Impulse Synaptic Transmission

Homeostasis Homeostasis is the state of relative stability within the bodyHomeostasis is the state of relative stability within the bodyHomeostasis Homeostasis is achieved through negative feedback mechanismsHomeostasis is achieved through negative feedback mechanisms Homeostasis regulates such factors as blood pressure, body temperature, blood glucose concentration and many other processesHomeostasis regulates such factors as blood pressure, body temperature, blood glucose concentration and many other processesbody temperatureblood glucose concentrationbody temperatureblood glucose concentration The nervous system and endocrine system control homeostasisThe nervous system and endocrine system control homeostasisnervous

Organization of the Nervous System The nervous system is made up of two divisions:The nervous system is made up of two divisions:nervous systemnervous system 1.The central nervous system (CNS) consists of the brain and spinal cord CNS 2.The peripheral nervous system (PNS) consists of somatic and autonomic nerves somatic and autonomic nervessomatic and autonomic nerves

Cells of the Nervous System The nervous system consists of neurons and glial cellsThe nervous system consists of neurons and glial cellsneurons and glial cellsneurons and glial cells Neurons are the basic functional units of the nervous systemNeurons are the basic functional units of the nervous system Glial cells physically support the fragile neuronsGlial cells physically support the fragile neurons Neurons are organized into bundles called nervesNeurons are organized into bundles called nerves nerves

Cells of the Nervous System There are three types of neuronsThere are three types of neurons 1.Sensory neurons carry nerve impulse from receptors to the central nervous system Sensory neuronsSensory neurons 2.Interneurons carry nerve impulses within the central nervous system Interneurons 3.Motor neurons carry nerve impulses from the central nervous system to the effectors (muscles or glands) Motor neuronsMotor neurons

Cells of the Nervous System Neurons relay nerve impulses along neural pathways to create either cognitive responses or reflex responsesNeurons relay nerve impulses along neural pathways to create either cognitive responses or reflex responses cognitive responses or reflex responses cognitive responses or reflex responses

The Nerve Impulse A nerve impulse is an electrochemical charge that travels along the length of a neuronA nerve impulse is an electrochemical charge that travels along the length of a neuronelectrochemical chargeelectrochemical charge Nerve impulse transmission involves several stepsNerve impulse transmission involves several steps 1.Resting membrane potential is established so the neuron is polarized Resting membrane potentialResting membrane potential 2.The neuron is stimulated above its threshold potential

The Nerve Impulse 3.An action potential is created at one point on the membrane so that part of the neuron is depolarized action potentialaction potential 4.The depolarized zone cascades along the neuron towards the axon terminals cascades 5.The neuron repolarizes to establish resting potential once again A nerve impulse can be represented by a graphA nerve impulse can be represented by a graphgraph

Synaptic Transmission Once the nerve impulse reaches the axon terminal of the presynaptic neuron it must cross the synapse to the dendrite of the postsynpatic neuronOnce the nerve impulse reaches the axon terminal of the presynaptic neuron it must cross the synapse to the dendrite of the postsynpatic neuron cross The gap between neurons is called a synapseThe gap between neurons is called a synapsesynapse The gap between a motor neuron and a muscle fiber is called a neuromuscular junctionThe gap between a motor neuron and a muscle fiber is called a neuromuscular junction

Synaptic Transmission The nerve impulse crossing the synapse involves several stepsThe nerve impulse crossing the synapse involves several stepsseveral stepsseveral steps 1.The depolarized zone reaches the axon terminal of the presynaptic neuron which triggers vesicles to migrate towards the synapse 2.The vesicles release neurotransmitters into the synapse

Synaptic Transmission 3.The neurotransmitters diffuse across the synapse to receptors on the postsynaptic neuron 4.Ion channels on the postsynaptic neuron open to cause either depolarization or hyperpolarization of the membrane

Synaptic Transmission Excitatory neurotransmitters open sodium channels and cause depolarization while inhibitory neurotransmitters open potassium channels and cause hyperpolarizationExcitatory neurotransmitters open sodium channels and cause depolarization while inhibitory neurotransmitters open potassium channels and cause hyperpolarizationExcitatoryneurotransmittersExcitatoryneurotransmitters Acetylcholine is an excitatory neurotransmitter that must be broken down by an enzyme (cholinesterase) so that the postsynaptic neuron can repolarizeAcetylcholine is an excitatory neurotransmitter that must be broken down by an enzyme (cholinesterase) so that the postsynaptic neuron can repolarizecholinesterase

Synaptic Transmission Summation is the combined effect of all neurotransmitters from the pre- synaptic neurons on the post-synapatic neuronSummation is the combined effect of all neurotransmitters from the pre- synaptic neurons on the post-synapatic neuronSummation

Central Nervous System The Spinal Cord The Brain

The Spinal Cord The spinal cord is a column of nerve tissue that extends out of the skull from the brain and downward through a canal within the back boneThe spinal cord is a column of nerve tissue that extends out of the skull from the brain and downward through a canal within the back bonespinal cordspinal cord The spinal cord is protected by the vertebrae of the backboneThe spinal cord is protected by the vertebrae of the backbonevertebrae Spinal nerves contain sensory and motor nerves carry impulses into and out of the spinal cord, respectivelySpinal nerves contain sensory and motor nerves carry impulses into and out of the spinal cord, respectivelySpinal nervesSpinal nerves

The Spinal Cord The dorsal root of each spinal nerve contains sensory neuronsThe dorsal root of each spinal nerve contains sensory neurons The ventral root of each spinal nerve contains motor neuronsThe ventral root of each spinal nerve contains motor neurons The cells of the spinal cord are either grey matter or white matter and are protected by the cerebrospinal fluid and the meningesThe cells of the spinal cord are either grey matter or white matter and are protected by the cerebrospinal fluid and the meningescerebrospinal fluid meningescerebrospinal fluid meninges

The Brain The brain is subdivided into three regionsThe brain is subdivided into three regionsbrainregionsbrainregions 1.Forebrain: consists of the thalamus, hypothalamus, corpus callosum and cerebrum 2.Midbrain: consists of neurons that relay impulses between the forebrain and the hindbrain 3.Hindbrain: consists of the cerebellum, medulla oblongata and pons

The Brain The cerebrum is the conscious part of the brainThe cerebrum is the conscious part of the brain The surface of the cerebrum is called the cerebral cortexThe surface of the cerebrum is called the cerebral cortex cerebral cortex cerebral cortex The cerebral cortex is divided into hemispheresThe cerebral cortex is divided into hemispheres The hemispheres are connected through the corpus callosumThe hemispheres are connected through the corpus callosum corpus callosum corpus callosum Each hemisphere is divided into four lobes (parietal, temporal, frontal and occipital)Each hemisphere is divided into four lobes (parietal, temporal, frontal and occipital)lobes

Peripheral Nervous System The Somatic System The Autonomic System

The Somatic System The somatic nervous system:The somatic nervous system: 1.Under voluntary control 2.Controls the skeletal muscles of the head, torso and limbs 3.Includes spinal nerves and most cranial nerves spinal nerves cranial nervesspinal nerves cranial nerves

The Autonomic System The autonomic nervous system:The autonomic nervous system: 1.Under involuntary control 2.Controls the cardiac and smooth muscles of the circulatory, respiratory, excretory, endocrine and digestive systems 3.Comprised of two divisions two divisionstwo divisions a)Sympathetic: prepares the body for stress b)Parasympathetic: returns the body to normal after stress