define coordination
stimuli being detected by receptors so the organism responds using effectors
which 2 systems do the communication between receptors and effectors
1-nervous coordination
2-endocrine/ hormonal coordination
the human nervous system is divided to 2 systems state them and what they contain
its divided into
1-central nervous system which contains brain, spinal cord and relay neurons, sensory neurons and motor neurons
2- peripheral nervous system which contains cranial and spinal neurons which connect brain and spinal cord with other organs in the body and sensory and motor neurons
how is nervous coordination done
using electrical impulses
define electrical impulse
an electrical signal that passes along nerve cells called neurons
state the 3 types of neurons and their function
1- sensory neuron ; carries impulses from receptor to CNS
2- relay neuron; carries impulses from sensory neuron to motor neuron within CNS
3-motor neuron; carries impulses from CNS to effectors
state the structure of neurons and function of each part
1- dendrites; connect with other neurons to receive impulses
2-cell body; holds nucleus, cytoplasm and other organelles
3-axon; carries impulses away from cell body
4- myelin sheath; -insulates axon, -increases speed of transmission and prevents leakage of impulse
5-axon terminals; connects with muscles to deliver impulses
state the adaptations of neurons
1-long axons to transmit impulses over long distances
2-myelin sheath to insulate axon and increase speed of transmission
3-many mitochondria to provide energy for transmission of electrical impulses
define reflex action and state what’s meant by reflex arc
-automatic rapid response to stimuli to protect body from dangerous stimuli
-its a pathway taken by a nerve impulse during reflex actions
state 5 examples of reflexes
1-blinking
2-pupil reflex
3-withdrawal reflex
4-knee jerk
5-coughing and sneezing
compare between voluntary and involuntary actions
1-voluntary actions; slower, needs thinking so are controlled by brain and response varies
2-involuntary actions; faster, dont need thinking so are controlled by spinal cord, fixed response
what is a synapse and how does transmission across a synapse occur
-synapse; a gap between two neurons
-impulse reaches axon terminals
-vesicles containing neurotransmitters are released
-vesicles release neurotransmitters which diffuse across synapse
-neurotransmitters bind to receptors on the next neuron
-impulse continuous in the next neuron
why does transmission take more time than expected
due to delay at synapse, release of neurotransmitters and thinking process in the brain
state what is meant by sense organ
its an organ that contains a group of receptor cells which are sensitive to a certain kind of stimulus
-receptors work by converting a certain type of energy into electrical impulses, eg; the eye converts light energy into electrical impulses that are received by the brain
define hormones
chemical substances that are released by endocrine glands directly into the blood that alter the activity of one or more organs and are destroyed by the liver after
define endocrine glands
they are ductless glands that release hormones directly into the bloodstream by diffusion
define exocrine glands
they are glands which release their products through duct such as salivary glands
define adrenaline
its a hormone secreted by adrenal glands in fear or flight situations or during vigorous activities to provide the body with more energy
state the effects of adrenaline
1-increases heart rate to provide more oxygen to muscles to release more energy and remove co2
2-increases breathing rate to obtain more oxygen and remove co2
3-widens pupil to allow more light to enter the eyes
4-breaks down glycogen stored in liver into glucose so more glucose enters the blood to reach the muscles to release energy
5- causes arterioles in gut and skin to constrict and arterioles in muscles to dilate so more blood diverts to muscles
comparison between nervous and hormonal control
endocrine; -transmission of chemicals
-transmission via blood
-slow response
-hormones dispersed throughout the body
-long term effect
nervous; -transmission of electrical impulses
-transmission via nerves
-rapid response
-impulses only sent to directed organ
-short lived effect
define homeostasis
maintenance of constant internal environment regardless of the external environment
give 3 examples of homeostasis
1-temperature; to provide optimum temperature and prevent their denature so metabolism doesn’t slow down
2-osmoregulation ; regulating water potential of the blood to prevent dehydration or bursting of the cells
3-blood glucose level; if blood glucose level increases it leads to diabetes, if it decreases it will cause low energy and fatigue
what is negative feedback
1-if blood glucose or body temperature change these changes are detected by receptors , signals are sent to effectors which restore them to the normal level
2- once normal level is restored effectors stop working to avoid overcorrection
3-body temperature and blood glucose aren’t constant but they must be maintained within set limits
what happens in thermoregulation
-normal body temperature is kept within 37 degrees as its optimum for enzymes to avoid their denature as they’re needed to catalyze chemical reactions in the body
-changes in temperature are detected by thermoreceptors in hypothalamus and receptors in skin which send impulses to receptors until normal body temperature is restored
