27.4 The Autonomic Nervous System INVOLUNTARY RESPONSES - responses that do not involve the brain (cerebrum): unconscious, independent of external stimuli,

27.4 The Autonomic Nervous System

INVOLUNTARY RESPONSESINVOLUNTARY RESPONSES

- responses that do not involve the brain - responses that do not involve the brain (cerebrum):(cerebrum):

unconscious, independent of external stimuli,unconscious, independent of external stimuli,- controlled by the ANS (autonomic nervous - controlled by the ANS (autonomic nervous

system) which consists of two branches:system) which consists of two branches: 1. sympathetic nervous system1. sympathetic nervous system 2. parasympathetic nervous system2. parasympathetic nervous system- examples: heart beat, peristalsis, prepare for - examples: heart beat, peristalsis, prepare for

emergenciesemergencies

27.4 The Autonomic Nervous System

Effects of the sympathetic & parasympathetic Effects of the sympathetic & parasympathetic nervous systems are nervous systems are antagonisticantagonistic..

The balance between the two systems accurately The balance between the two systems accurately regulates the involuntary activities of glands and regulates the involuntary activities of glands and organs. organs.

Training is possible to control consciously Training is possible to control consciously certain activities, e.g. urination & defaecationcertain activities, e.g. urination & defaecation

TABLE 27.1 Comparison of some effects of TABLE 27.1 Comparison of some effects of sympathetic & parasympathetic branchessympathetic & parasympathetic branches

Sympathetic nervous systemSympathetic nervous system Parasympathetic nervous Parasympathetic nervous systemsystem



increases cardiac outputincreases cardiac output



increases cardiac outputincreases cardiac output decreases cardiac outputdecreases cardiac output




increases blood pressureincreases blood pressure




increases blood pressureincreases blood pressure decreases blood pressuredecreases blood pressure





dilates bronchiolesdilates bronchioles





dilates bronchiolesdilates bronchioles constrict bronchiolesconstrict bronchioles






increases ventilation rateincreases ventilation rate






increases ventilation rateincreases ventilation rate decreases ventilation ratedecreases ventilation rate







dilates pupils dilates pupils







dilates pupils dilates pupils constrict pupilconstrict pupil



contracts anal & bladder contracts anal & bladder sphincterssphincters




relaxes anal & bladder relaxes anal & bladder sphincterssphincters





contracts erector pili musclescontracts erector pili muscles





contracts erector pili musclescontracts erector pili muscles no comparable effectno comparable effect






increases sweat productionincreases sweat production






increases sweat productionincreases sweat production no comparable effectno comparable effect







no comparable effectno comparable effect







no comparable effectno comparable effect increases secretion of tearsincreases secretion of tears

27.5 The Central Nervous System27.5 The Central Nervous System

- consists of the brain and the spinal cord- consists of the brain and the spinal cord

How the CNS is protected and nourished ?How the CNS is protected and nourished ?- the brain is protected by the the brain is protected by the craniumcranium, while the , while the

spinal cord is protected by the spinal cord is protected by the vertebral columnvertebral column- both are both are bonybony tissues tissues

- - meningesmeninges covering the whole CNS covering the whole CNS

- cavities between meninges, ventricle of brain, - cavities between meninges, ventricle of brain, central canal of spinal cord are filled with central canal of spinal cord are filled with

cerebrospinal fluidcerebrospinal fluid for for

1 nourishment and removal of wastes1 nourishment and removal of wastes

2 absorbing shock 2 absorbing shock

3 maintaining the shape of the brain3 maintaining the shape of the brain

27.5.1 The Spinal Cord27.5.1 The Spinal Cord- a - a reflex centrereflex centre for controlling involuntary actions such for controlling involuntary actions such

as knee jerk;as knee jerk;- transmits impulses to and from the brain- transmits impulses to and from the brain

PERIPHERAL NERVOUS SYSTEMPERIPHERAL NERVOUS SYSTEM- consists of the cranial nerves and spinal nerves- consists of the cranial nerves and spinal nervesCranial NervesCranial Nerves- 12 pairs from medulla oblongata to sense organs in the - 12 pairs from medulla oblongata to sense organs in the

head & neckhead & neckSpinal NervesSpinal Nerves- 31 pairs in man, running from spinal cord to body trunk - 31 pairs in man, running from spinal cord to body trunk

& limbs& limbs- all are mixed nerves - all are mixed nerves - dorsal rootdorsal root for sensory nerve fibres; with a for sensory nerve fibres; with a dorsal root dorsal root

ganglionganglion of cell bodies of cell bodies- ventral rootventral root for motor nerve fibres; cell bodies in grey for motor nerve fibres; cell bodies in grey

matter of spinal cordmatter of spinal cord

Longitudinal section through a human brainLongitudinal section through a human brain

27.5.2 Structure of The Brain27.5.2 Structure of The Brain

Neurones in the brainNeurones in the brain

Neucleus Dentrite Cell body

27.5.2 Structure of The Brain27.5.2 Structure of The Brain & & 27.5.3 Functions of The Brain27.5.3 Functions of The BrainRegions and Functions of the BrainRegions and Functions of the Brain- The brain is divided into 3 regions: - The brain is divided into 3 regions: the forebrain, midbrain & the hindbrainthe forebrain, midbrain & the hindbrain

1. The Forebrain1. The Forebrain - - cerebrumcerebrum is divided into two is divided into two cerebral hemispherescerebral hemispheres connected by nerve connected by nerve

fibresfibres- surface is- surface is foldedfolded to increase the surface area for to increase the surface area for increased co-increased co-

ordinationordination - - centrecentre for thinking, memory, reasoning, imagination, learning & for thinking, memory, reasoning, imagination, learning &

voluntary actionsvoluntary actions

Map of the major regions of the cerebral cortex Map of the major regions of the cerebral cortex and their functionsand their functions

- - sensory areassensory areas receive impulses from the receptors; receive impulses from the receptors; removal of these areas results in loss of the sensesremoval of these areas results in loss of the senses- - motor areasmotor areas send impulses to the effectors; send impulses to the effectors; if these areas are damaged, no responses will be evoked;if these areas are damaged, no responses will be evoked;- - association areasassociation areas correlate impulses from different correlate impulses from different

receptors and assist in producing the appropriate responsesreceptors and assist in producing the appropriate responses

2. The Midbrain2. The Midbrain- includes the optic lobes for vision- includes the optic lobes for vision- floor is the - floor is the hypothalamushypothalamus for homeostasis:for homeostasis: main controlling region for the autonomic main controlling region for the autonomic

nervous system;nervous system; two centres (two centres (sympatheticsympathetic & & parasympatheticparasympathetic);); controls complex patterns of behaviour such as controls complex patterns of behaviour such as

feeding, sleeping;feeding, sleeping; monitor composition of blood;monitor composition of blood; acts as an endocrine gland acts as an endocrine gland

3. The Hindbrain3. The Hindbrain

- - cerebellumcerebellum:: a centre for a centre for muscular co-ordinationmuscular co-ordination and and body balancebody balance

- medullar oblongatamedullar oblongata:: the the reflex centrereflex centre for controlling for controlling involuntary actionsinvoluntary actions such as such as breathing, heartbeat, breathing, heartbeat, swallowing, coughing, sneezing, and salivationswallowing, coughing, sneezing, and salivation;;

- damage of the medulla oblongata may lead to deathdamage of the medulla oblongata may lead to death

Internal Structure of the BrainInternal Structure of the Brain- - grey mattergrey matter:: outsideoutside the brain; consists of the brain; consists of

nerve nerve cell bodiescell bodies onlyonly- - white matterwhite matter:: insideinside the brain; consists of the brain; consists of

nerve fibresnerve fibres only only** In medulla oblongata & spinal cord, the In medulla oblongata & spinal cord, the

distribution of grey and white matters is the distribution of grey and white matters is the reversereverse

27.6 Sensory Perception27.6 Sensory PerceptionReceptorsReceptors are sensitive to stimuli, some have become are sensitive to stimuli, some have become

highly specialized to detect a particular form of energy highly specialized to detect a particular form of energy and give out response into a nervous impulse, they act as and give out response into a nervous impulse, they act as biological transducersbiological transducers..

Primary sense cellsPrimary sense cells is a simple receptor with dendrite is a simple receptor with dendrite receives the stimulus & creates an action potential to the receives the stimulus & creates an action potential to the remainder of the nervous system, e.g. conesremainder of the nervous system, e.g. cones

Secondary sense cellsSecondary sense cells outside the nervous system pass outside the nervous system pass chemical or electrical messages to a neuron to create an chemical or electrical messages to a neuron to create an action potential, e.g. taste cells of tongueaction potential, e.g. taste cells of tongue

ExterioceptorsExterioceptors collect information from the external collect information from the external environmentenvironment

InteroceptorsInteroceptors collect information from the internal collect information from the internal environmentenvironment

ProprioceptorsProprioceptors provide information on the relative position provide information on the relative position & movements of muscles& movements of muscles

Classification according to the form of energyClassification according to the form of energy::

1.1.MechanoreceptorsMechanoreceptors - detect movements, pressures - detect movements, pressures and tensions, e.g. soundand tensions, e.g. sound

2.Chemoreceptors2.Chemoreceptors - detect chemical stimuli, e.g. - detect chemical stimuli, e.g. taste & smelltaste & smell

3.Thermoreceptors3.Thermoreceptors - detect temperature changes - detect temperature changes

4.Electroreceptors4.Electroreceptors - detect electrical fields (mainly - detect electrical fields (mainly fish)fish)

5.Photoreceptors5.Photoreceptors - detect light & some other forms - detect light & some other forms of electromagnetic radiationof electromagnetic radiation

MechanoreceptionMechanoreception- respond to mechanical stimuli: gravity, vibration & - respond to mechanical stimuli: gravity, vibration &

pressurepressure- examples: touch, pressure receptors, ear- examples: touch, pressure receptors, earChemoreceptionChemoreception- respond to taste & smell- respond to taste & smelltaste buds for sweet, sour, bitter & salt- taste buds for sweet, sour, bitter & saltFunctions in mammalsFunctions in mammals: : 1. Locating food & its acceptance or rejection1. Locating food & its acceptance or rejection2. Locating a mate2. Locating a mate3. Detecting its predators3. Detecting its predators4. Detecting dangers, e.g. fire4. Detecting dangers, e.g. fire5. Locating & marking territories5. Locating & marking territories

Documents

27.4 The Autonomic Nervous System INVOLUNTARY RESPONSES - responses that do not involve the brain (cerebrum): unconscious, independent of external stimuli,