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Unformatted text preview: non-compressible, the
pressure wave moves the membranes in the cochlea,
causing the hair cells to be stimulated. Skin Senses (page 90) 1. Forearm. 3. (a) Endocrine signalling, where a hormone is
carried in the blood between the endocrine gland/
organ where it is produced to target cells.
(b) Paracrine signalling, where cell signalling
molecules are released to act on target cells
in the immediate vicinity, e.g. at synapses or
between cells during development.
(c) Autocrine signalling, where cells produce and
react to their own signals (e.g. growth factors from
T cells stimulate the production of more T cells). 2. The three signalling types all have in common some
kind of chemical messenger or signal molecule
(ligand) and a receptor molecule (on the target cells,
which may or may not be on the cell producing the
signal). Lips and/or fingertips. 2. 1. The lips and/or fingertips need to be sensitive to
carry out their functions (locating and tasting food,
communication etc,). They therefore need to have a
great number of receptors. The forearm requires many
fewer as it is not involved in intricate tasks. Taste and Smell (page 91)
1. Chemical sense relies on the chemicals (scent
molecules) binding to membrane-bound sensory
receptors and inducing a change in membrane
potential in the sensory cell (signal transduction).
These electrochemical messages are relayed to
the appropriate centers in the brain where they are
interpreted. 2. Example only:
10 s: 1 (very strong)
20 s: 2 (quite strong)
30 s: 3 (noticeable)
40 s: 4 (weak)
50 s: 5 (very faint)
60 s: 6 (could not detect) 3. (a) The sense of smell (to that scent) declines.
(b) Sensory adaptation. The sensory cells adapt to
the stimulus and cease responding to it.
(c) It is adaptive to stop responding to stimuli that are
constantly present and do not change in intensity.
Appropriate responses are directed to new
stimuli. Hormonal Regulatory Systems (page 93)
1. (a) Antagonistic hormones: Two hormones that
have contrasting (counteracting) effects on Biozone International 2009 Photocopyin...
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- Winter '13