Why is is it important for organisms to respond to their external environment?

Why is it important for organisms to respond to their external environment?The environment provides many different stimuli. Organisms respond in a manner

that enables them to maintain homeostasis.

Regulation (life process) is maintained by the:

Nervous and Endocrine Systems

Hypothesize which system works the quickest in response to stimuli.

Regulation (life process) is maintained by the:

Nervous and Endocrine Systems

Hypothesize which system works the quickest in response to stimuli. nervous system- electrochemical impulses.

endocrine system- hormone release

Functional Cell in the Nervous System is the NEURON.

Neurons send Electrochemical Signals

Nervous Tissue Organization

Signal Transmissionis

Electrochemical Impulse.

Chemical in the Electrochemical

…but what’s going on in the axon?

Electrical in the Electrochemical

Resting Potential of a Neuron

Oscilloscope Reading

Action potential is an All-or-Nothing event once the nerve has been stimulated past the threshold.

So……How do you explain the differences in the following pains…

Weak pains? Strong pains? Intense pains?

Its simple……stimulation of more or less neurons.

Nervous System Organization

Organisms evolved from simple to complex.

Nervous systems went from being decentralized to centralized.

Decentralized Nervous System

Cephalization is accompanied by a concentration of nervous tissue (cephalic ganglion or brain) and feeding mechanisms in the head region that serves to integrate the activities of the nervous system.

Phylum: Cnidaria

•Nervous system•cephalization- not much

•nerve cells scattered around mouth•no organization or brain

•nerve net cells and sensory cells•sensitive to chemicals & touch•coordinate muscle fiber action•hormone glutathione produces feeding response

Why is a nerve net an inefficient design for more complex organisms?

Centralized Nervous System

Why is a nerve net an inefficient design for more complex organisms?The entire organism is responding to stimuli. This is a waste of energy.

Considering the structure of the Planaria (Platyhelminthes), how would you describe its nervous tissue organization?

•well-defined nervous system w/ sense organs•ganglia concentrated as simple brain at

head•sensory cells (statocysts sense gravity,

light sensory cells at eyespots, chemosensory cells)•2 nerve cords run length of body

Phylum: PlatyhelminthesClass: Turbellaria

Platyhelminthes are believed to be the first hunters- organisms that use their senses to acquire food.

Considering the structure of the Roundworms (Nematoda), how would you describe its nervous tissue organization?

Kingdom: AnimaliaPhylum: Nematoda (formerly Aschelminthes)

cross-section

•nervous system•sensory structures and ganglia at head•nerve ring with ganglia around the pharynx•ventral and dorsal nerve cords

Kingdom: AnimaliaPhylum: Nematoda (formerly Aschelminthes)

Considering the structure of the Mollusks, how would you describe its nervous tissue organization?

Visceral mass

Mantle

Foot

Coelom Intestine

Gonads

Mantlecavity

Anus

Gill

Nervecords Esophagus

Stomach

Shell

Radula

Mouth

Mouth

Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph.

Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces). The organs of the mollusc are thus continually bathed in hemolymph.

The long digestive tract is coiled in the visceral mass.

Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward-curved teeth slides back and forth, scraping and scooping like a backhoe.

The nervous system consists of a nerve ring

around the esophagus, from

which nerve cords extend.

Figure 33.16

Octopus Anatomy

The mantle cavity of a bivalve

Hinge areaGut Coelom

Heart

Adductormuscle

Anus

Excurrentsiphon

Waterflow

IncurrentsiphonGill

Mantlecavity

Foot

Palp

Mouth

Shell

Mantle

Considering the structure of the Earthworm (Annelid) and the Grasshopper (Arthropod), how would you describe its nervous

tissue organization?

Anatomy of the earthworm

Grasshopper Anatomy

Both organisms have cerebral ganglion that enable them to process information and respond.

Chordates: Most evolved phyla in the Animal Kingdom

Includes-

Fish, Amphibians, Reptiles, Birds, Mammals

• Notochord • an internal skeletal rod that provides support• lies ventral to the neural tube • Hollow nerve cord that lies dorsal to the notochord• Pharyngeal pouches • Disappear during development in mammals• linings give rise to many glands in the lymphatic

system: thymus, tonsils, carotid bones, parathyroid glands

• Postanal Tail (at some stage of development)

Characteristics of Chordates

Human Nervous System

Human Nervous System

• Central Nervous System • Peripheral Nervous System

Central Nervous System

• Brain– Sensory information is

received and motor control is initiated

– Parts of the Brain:• Brain stem- medulla,

pons, and midbrain• Diencephalon• Cerebellum• Cerebrum

• Spinal Cord– Sensory information is

received and motor control is initiated

– Parts of the spinal cord:• White matter- Myelinated

fibers• Gray matter- cell bodies

and unmyelinated fibers

The Human Brain

The Brain Stem

• Medulla Oblongota– Controls many involuntary actions (breathing, heart

rate, organ function, etc.)• Pons– Functions in regulating breathing– Reflex centers for head movements in response to

auditory and visual stimuli• Midbrain– Reflex centers for visual, auditory, and tactile

responses

Diencephalon

• Hypothalamus– Maintains homeostasis and contains centers for

regulating hunger, sleep, thirst, body temp, water balance and blood pressure

– Contains the pituitary gland (master gland for the endocrine system)

• Thalamus– Serves as a relay information for sensory information – Involved in arousal and higher mental functions

(emotion, memory, etc.)

Cerebellum

• Muscle coordination– Integrates impulses received from higher centers

to ensure that all of the skeletal muscles work together to smooth and graceful motions

– Maintains normal muscle tone and maintains posture

– Coordinates with the inner ear to maintain balance and body position

Cerebrum

• Largest part of the brain in humans• Receives sensory input for voluntary

movements• Higher thought processes (learning, memory,

speech, etc.)

Cerebral Hemispheres

• Frontal lobe: motor, speech, language

• Temporal lobe: Auditory

• Parietal lobe: Somatosensory processing, taste

• Occipital: Visual

Brain and Spinal Cord are protected by membranes.

Meninges

Peripheral Nervous System

• Somatic– Reflexes of the body in

response to sensory stimuli• Regulated by the spinal

cord and cranial nerves

– Voluntary Movements• Regulated by the brain

• Autonomic– Involuntary actions

• Regulated by the brain

The Reflex Arc involves the action of the following types of neurons:

How would you build the Reflex Arc?

Autonomic Nervous System

• Sympathetic • Parasympathetic

These two systems are antagonistic of each other. This property enables control of involuntary actions necessary for life functions.

Here is a specific example…..

Heart Rate Regulation