Integration of body systems

system integration

• complex living organisms evolved to make use of body systems made up of component parts that collectively perform an overall function

• coordination of parts required for systems to work together for whole organism

cells, tissues, organs and systems

• specialised cells of the same type group together to form tissues

• tissues work together to perform a particular function

• different tissues work together to form organs

• different organs work together to form organ systems

• organ systems work together to carry out the life functions of a complete organism

• each hierarchical level has great efficiency and complexity

emergent properties

• multicellular organisms can perform functions unicellular organisms cannot

• this is a result of properties emerging when individual cells organise and interact

integration of organs

• communication within bodies of animals primarily by nervous and endocrine system

• blood circulates throughout all organs and almost all tissues transporting these things e.g:

  • energy as respiratory substrates

  • oxygen

  • water and carbon compounds

  • waste products of metabolism

nervous system vs. endocrine system

similarities:

• both used for communication between cells

• both can work over long distances

• both use chemicals that bind to receptors

structure of brain

• cerebral cortex:

  • outer layer of brain, divided into 2 hemispheres

  • responsible for higher order processes (intelligence, memory

• cerebellum

  • underneath cerebral cortex

  • responsible for balance, muscle coordination and movement

• brainstem

  • relays messages between cerebral cortex, cerebellum and spinal cord

  • medulla: controls unconscious activities like heart beat

• important glands:

  • pituitary gland:

    • produces hormones

  • hypothalamus

    • region of brain that regulates body temp

role of brain: central info integration organ

• brain receives info, processes it, stores it and sends instructions to all parts of body to coordinate life processes

• info is received from sensory receptors, in specialised sense organs like eye or in other organs like pressure receptor in blood vessel

• brain also stores info for short/long term in form of memory

• processing info leads to decision making by brain, resulting in signals sent to effectors (muscles, glands)

spinal cord

• area of tissue in centre of spinal cord: grey matter, integrating centre for unconscious processes

• this info is processed at the unconscious level, involves reflex reactions, which happen quickly

input through sensory neurones

• receptors: specialised cell that detects changes in environment that cause stimulus

• receptors convert energy in one form into an electrical impulse, and pass to sensory neurone

• signals from sensory neurones are conveyed to CNS

  • spinal cord receives signals from organs like skin and muscle

  • brain receives signals from all the sense organs located in head

    • sensory inputs are receives by cerebral hemispheres

output through motor neurones

• motor cortex can send impulses to any striated muscle (attached to bone) in the body

• motor neurones: used to carry out action potentials to muscles to initiate movement

• motor neurone receives signals from interneurone, forms synapse with second motor neurone, whose axon leads to a specific striated muscle

• when nerve impulse reaches the end, contraction is stimulated

structure of nerves

• nerves are made of bundles of sensory neurones/motor neurones fibres

  • may be myelinated or unmyelinated

  • protective myelin sheath

reflex arc

• pathway along which impulses are transmitted from a receptor to an effector without involving conscious regions of the brain

• synapses for pain reflex are in spinal cord

order of a reflex arc

• (pain) reflex arc in the hand:

  • stimulus may be sharp pin or heat, detected by receptor in the skin of the hand, pain is perceived directly by nerve endings of sensory neurone

  • nerve impulse from receptor cell/sensory nerve endings passed to CNS

  • electrical impulse passed to interneuron in grey matter of brain/spinal cord

    • process signals brought by sensory neurone and make decisions abt appropriate responses

  • interneuron passes synapse to appropriate motor neurone. if threshold potential achieved, impulse is passed along axon to effector

  • when stimulated by motor neurone, effector (muscle) will contract and pull away from stimulus

role of cerebellum

• coordinates movement and controls skeletal muscle contraction and balance

• does not initiate movement, when movement begins the cerebellum receives feedback signals from area of the body that’s moving and it sends signals to coordinate and control the movement

circadian rhythms

• 24 hour cycles

melatonin and sleep patterns

• melatonin controls sleep-wake circadian rhythm

• pineal gland secretes melatonin into blood

  • production is influenced by detection of light/dark by retina in eye

  • signals transmitted to pineal gland according to amount of daylight person is exposed to

• increasing melatonin: tiredness, decreasing melatnonin: awakeness

epinephrine

• during stressful, fearful or exciting situations, neurones stimulate epinephrine secretion

• since it is hormone, transported around body in bloodstream and binds to receptors on target organs, one of which is SAN, leading to increased frequency of excitations

  • increases heart rate to supply blood to muscle cells faster

  • increases rate of aerobic respiration, so more energy

• due to this, striated muscles receive a greater vol of blood per min, blood carries more glucose and oxygen allowing increased production of ATP, thus more powerful/frequent muscle contractions

• changes experienced are both nervous and hormonal responses

control of endocrine system

• hypothalamus

  • monitors blood as it flows through the brain, releases hormones in response or stimulate pituitary gland to release hormones

  • examples of functions:

    • regulating body temp

    • osmoregulation

• pituitary gland

  • located below hypothalamus

  • produces a range of hormones

feedback control of heartrate

• medulla oblongata: cardioregulatory centre in the brain, unconscious control

  • found at the base of brain near top of spinal cord

  • causes a change in heart rate to bring pressure, pH and conc of O2/CO2 in blood to be brought back to target levels

  • signals sent to the SAN cause the heart rate to be changed

• exercise can cause internal stimuli, detected by chemoreceptors and baroreceptors, located in the aorta and in the carotid arteries

  • chemoreceptors: detect changes in blood pH and O2 and CO2 levels

  • baroreceptors monitor changes in blood pressure

feedback control of ventilation rate

• controlled by respiratory centres in brainstem

  • processes inputs and changes ventilation rate by negative feedback if blood pH is too high/low

• during exercise, high levels of CO2 produced due to increase in respiration, so blood pH falls

• pH changes in the blood:

  • CO2 released as a waste product from respiring cells diffuses into cytoplasm of red blood cells

  • CO2 combines with water forming carbonic acid which dissociates readily into H+ and HCO3-

  • H+ ions lower pH of blood so their presence detected by chemoreceptors in the medulla

  • signals sent at higher rate to diaphragm and EIC muscles to increase ventilation rates and volume of air being moved in/out of lungs

control of peristalsis

• peristalsis: series of muscles contractions in walls of oesphagus or small intestine, controlled unconsciously by enteric nervous system (ENS)

• peristalsis controlled by muscles which initiate peristaltic reflex

  • muscle in tongue is under voluntary control by brain and initiates swallowing

  • bolus of food is detected by stretch receptors (sensory neurones of ENS) as alimentary canal becomes distended

  • signals from these receptors pass to brainstem, which stimulates muscle contractions that push food into oesophagus, now the process is involuntary

  • defecation is the removal of faeces from the rectum via anus. anus relaxes and widens to defecate, this process is voluntary

observations of tropic responses

• tropisms: responses to factors affecting plant growth

  • towards a stimulus: positive, away from a stimulus: negative

  • most roots are positively gravitropic

• tropisms can be investigated and the responses to a variety of stimuli can be measured through:

  • qualitative diagrams of seedling growth

  • quantitative measurements of angles of curvature of seedlings

phototropism

• plant shoots are positively phototropic, they grow towards light

• ensures plants maximise the amount of light absorbed for photosynthesis

• affects shoots and top of stems

phytohormones in plant

• phytohormones: plants hormones that regulate growth, development, and response to stimuli

• e.g auxin resulting in cell elongation

maintaining phytohormone conc gradients

• auxins: group of plant hormone that influence many aspects of plant growth

• auxin enters cells by simple diffusion, but to exit and move to next cell it needs membrane proteins called auxin efflux carriers

• plant cells distribute auxin efflux carriers on one side of the cell to encourage one way movement of auxin

• process requires ATP

• efflux carriers are important in establishing auxin gradient across stem/root in response to stimulus

cell growth by auxin

• concentration of auxin determines the rate of cell elongation within the stem

• when light shines on stem from one side, an auxin gradient is establish with more auxin on the shaded side and less on illuminated side

• cell elongates faster on the shaded side, shoot bends towards the source of light

controlling growth by elongation

• auxin promotes synthesis of proton pumps by cell and their insertion into plasma membrane

• pumps transport H+ ions from inside the cell to the cell wall (apoplast), acidifying the apoplast

• cell wall made of cellulose contains crosslinkages, which are influenced by pH. more acidic pH weakens the links allowing wall to extend, so the cell can grow

• concentration gradients of auxin cause gradients of apoplastic pH and therefore difference in cell growth, needed for phototropism

interactions between auxin and cytokinin

• auxin: cell elongation, produced in shoots

• cytokinin: cell division, produced in roots

• both hormones must be transported to areas of the plant where they are not produced

  • cytokinin: from root to shoot

  • auxin: from shoot to root

• at certain concentrations, 2 hormones work together to ensure root and shoot growth is regulated

positive feedback in fruit ripening

• ethylene is a gas produced by fruit during fruit ripening, and produce this phytohormone as they ripen, so this is positive feedback that promotes rapid ripening

• gas diffuses from one fruit to adjacent fruit which triggers further release of ethylene

• effect is that all fruit ripens at the same time