• When the stimulation of a receptor results ina spontaneous, involuntary reaction, it iscalled reflex action or simply reflex.
SPINAL REFLEX ACTION• The reflexes of this type which involve only thespinal cord are called spinal reflexes.• Please note that when we lift a hot plate, thenalong with heat, the pain produced by heat alsoacts as a stimulus.• Most of the reflex actions involve only the spinalcord. They are called spinal reflexes.
BRAIN REFLEX ACTION• Reflex actions which involve brain are calledcerebral reflexes.• Cerebral reflexes occur in the organs present in thehead because these organs are directly connectedto the brain.• Example. Our eyes are present in the head. In dimlight, the pupil (a hole in the front of eye) is large sothat more light can enter into the eye and make ussee properly even in dim light.
Reflex arc• Rather than think about the sensation of heat ifthe nerves detect heat were to be connected tothe nerves that move muscles in a simpler way,the process of detecting the signal or the inputand responding to it by an output action might becompleted quickly. Such connections commonlycalled as reflex arc.
Group activity• Group A• Define reflex action.• Group B• Components of reflex action.• Group C• Discuss the process of reflex action.
The CerebrumPart I:Lobes, the Cerebral Cortex, andCortical Regions of the Brain
Cerebrum -The largest division of the brain. It isdivided into two hemispheres, each of which isdivided into four lobes.CerebrumCerebrumCerebellumhttp://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif
Cerebral CortexCerebralCortexCerebral Cortex - The outermost layer of graymatter making up the superficial aspect of thecerebrum.http://www.bioon.com/book/biology/whole/image/1/1-6.tif.jpg
Lobes of the Brain (4)• Frontal• Parietal• Occipital• Temporalhttp://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Lobes of the Brain - Frontal• The Frontal Lobe of the brain is located deep to theFrontal Bone of the skull.• It plays an integral role in the following functions/actions:- Memory Formation- Emotions- Decision Making/Reasoning- PersonalityModified from:
Lobes of the Brain - Parietal Lobe• The Parietal Lobe of the brain is located deep to theParietal Bone of the skull.• It plays a major role in the following functions/actions:- Senses and integrates sensation(s)- Spatial awareness andperception(Proprioception - Awareness ofbody/ body parts in space andin relation to each other)
Lobes of the Brain – Temporal Lobe• The Temporal Lobes are located on the sides of thebrain, deep to the Temporal Bones of the skull.• They play an integral rolein the following functions:- Hearing- Organization/Comprehension oflanguage- InformationRetrieval (Memory andMemory Formation)Modified from:http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Lobes and Structures of the BrainB.A.C.D.E.F.G.http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif
Group activity• Group A• What do you mean by CNS?• Group B• Give the components of peripheral nervoussystem.• Group C• Distinguish between voluntary and involuntaryaction.
Brain has 3 regions• Fore- Brain - cerebrum, thalamus, andhypothalamus (part of the limbic system).• Mid-brain - The midbrain consists of the tectumand tegmentum.• Hind-brain - cerebellum, pons and medulla. Oftenthe midbrain, pons, and medulla are referred totogether as the brainstem.
Fore- brain• The forebrain is divided into 2 halves – the right and leftcerebral hemispheres.• The cerebral hemispheres control your movement,thinking, memory, emotions, senses and speech.• As the nerve fibres leave the brain, they cross over fromone side to the other.• This means that the nerves that come from the rightside of your brain control the left side of your body.• Each hemisphere is divided into 4 areas called the
• The frontal lobe contains areas that control yourpersonality, thought, memory and behaviour.• Towards the back of the frontal lobe are areas thatcontrol movement and feeling.• The temporal lobe helps to control behaviour,memory, hearing, sight and your emotions.• The parietal lobe is mainly to do with language. It isresponsible for your speech, reading, writing orunderstanding of words.• The occipital lobe is the visual centre of the brain.
Functions• Cerebellum - This structure is associated withregulation and coordination of movement, posture,and balance.• Brain Stem: This structure is responsible for basicvital life functions such as breathing, heartbeat, andblood pressure.
How brain tissues are protected?• The brain is protected by a series of bone, membrane, and fluid.• The outermost protection is the cranium, or skull, which protectsthe brain from blows that could easily damage it.• Then there are three membranes called meninges.• Then brain is protected by a clear liquid called cerebrospinal fluid.This forms a cushion between the soft brain tissue and the hardcranial bones. This same fluid also fills spaces inside the brain.• Tissues inside the spaces produce cerebrospinal fluid, which flowthrough the spaces between the membranes.
Coordination in plants• Chhui mui or touch- me -not plant or sensitive plant• Mimosa family
Two different types of movement in plants• 1. Growth dependent movement• 2. Growth independent movement
• Immediate response ……• No nervous tissues/ muscle tissues involved in plantbody.• Plants undergo cell to cell communication systemdifferent from nervous system and muscular systemin animals.• They use chemical signals followed by cells swellingdue to uptake of more water and shrinking of cellsdue to loss of water from plant cells. So the cellshapes change due to response.
• Movement due to growth• Tendrils are plants that climb up on other plants orfences.• When tendrils come in contactwith any support, the part of●Tendril which is in contact withobject does not grow as rapidly asaway from the object or support.THIS MAKES TENDRILS TO CLING ORCOIL AROUND SUPPORT.
• Environmental triggers such as light, or gravity willchange in the directions that plant parts grow in.
The endocrine systemHormones :A hormone is a chemical released by a cellor a gland in one part of the body that sendsout messages that affect cells in other partsof the organism.Only a small amount of hormone is required.It is a chemical messenger that transports asignal from one cell to another.Hormones –secreted by ductless glands.Directly secreted into blood and lymph.
Endocrine systemHormones are produced and secreted byglands in the endocrine system.It consists of various endocrine glands.These glands do not have ducts (tubes) fortransporting chemical signals from one partof the body to another. So, they are referredas DUCTLESS GLANDS.Target organs: The organs responds tohormones.
Hormone producing glands and their secretionsGland Location Secretion FunctionThyroid Neck Thyroxin Controls metabolic rateAdrenal AbovekidneysAdrenalin Prepares body foremergency.Pancreas Abdomen Insulin,glucagonRegulates sugar level inblood.Testes Lowerabdomen(male)Testosterone Controls sexualdevelopment.Ovaries Lowerabdomen(female)Oestrogen Controls sexualdevelopment.Pituitary Brain Growth hormonestimulatinghormonesSpeeds up growth,activates other glands.